Investor–State Arbitration 2025 Comparisons

Spain is a signatory to multiple bilateral investment treaties (BITs) and multilateral agreements and has been one of the most prominent respondent states globally, particularly under the Energy Treaty Charter (ECT). Following its rollback of renewable energy subsidies between 2010 and 2014, Spain faced more than 50 arbitration claims under the ECT (totalling more than EUR10 billion).

Spain has consistently argued that the 2010–2014 renewables economic regime changes were necessary, proportionate, and in line with public interest, especially regarding energy market stability, and has challenged several awards in annulment proceedings, particularly under the International Centre for Settlement of Investment Disputes (ICSID). Spain has been ordered to pay hundreds of millions of euros in damages, though many awards remain unpaid or under challenge. Following the Achmea, Komstroy and PL Holdings rulings from the Court of Justice of the European Union (CJEU), Spain – alongside the European Commission – argues that intra-EU arbitration under the ECT is invalid.

Spain has taken a clear and evolving stance on investor–state arbitration (ISA), especially in the context of intra-EU BITs and the ECT. Spain’s policy has shifted significantly in recent years, driven by EU legal developments and its own experience as a frequent respondent in arbitration cases.

• On 5 May 2020, Spain joined 22 other EU member states in signing the Agreement for the Termination of Bilateral Investment Treaties Between the Member States of the European Union, a move that was a direct consequence to the Achmea judgment, which held that ISA clauses in intra-EU BITs are incompatible with EU law. The termination agreement covers approximately 130 intra-EU BITs, including Spain’s treaties with countries like Germany, France, and the Netherlands.
• Spain withdrew from the ECT, notifying its withdrawal on 16 April 2024, which took effect one year later, on 17 April 2025. The decision was taken by the Spanish government in view of the difficulty of modernising the treaty and its incompatibility with the EU’s energy and climate policy objectives, such as the European Green Deal.

Spain’s actions reflect a broader EU trend toward reclaiming regulatory sovereignty and limiting investor privileges that conflict with public policy. For investors, this means:

• reduced treaty protection within the EU;
• greater reliance on domestic legal remedies; and
• heightened scrutiny of arbitration clauses in future treaties.

Spain’s experience underscores the importance of assessing regulatory stability, especially in sectors like energy, infrastructure, and telecoms.

Spain is a committed participant in the international arbitration framework and is party to the following conventions that govern the recognition and enforcement of arbitral awards.

• Convention on the Recognition and Enforcement of Foreign Arbitral Awards (New York Convention). Spain signed the New York Convention with no reservations or declarations (meaning it is applied broadly, including awards from non-member countries). Spanish courts are generally supportive of enforcing foreign arbitral awards, provided procedural and public policy requirements are met.
• ICSID Convention, which enables arbitration under its auspices. Spain has been involved in numerous ICSID cases, especially in the wake of its renewable energy reforms. It has also participated in annulment proceedings and enforcement challenges under ICSID rules.
• European Convention on International Commercial Arbitration (Geneva Convention). Though largely superseded by the New York Convention, it still applies in specific contexts and complements Spain’s arbitration regime.

Spain’s jurisdiction offers a plurality of mechanisms for resolving disputes, and the choice often depends on their nature, the parties involved, and the applicable treaty or contract. Investors do not always default to arbitration. Their choice depends on treaty provisions (some BITs mandate arbitration), nature of dispute (regulatory vs contractual), cost and duration (arbitration may be faster but more expensive), enforceability (arbitration awards are often easier to enforce abroad) and political sensitivity (litigation may be preferred for public law issues).

Spain’s Arbitration Act is based on the UNCITRAL Model Law, making it attractive for both domestic and international arbitration. Spanish courts generally support arbitration and enforce awards under the New York Convention. Arbitration is often favoured for its speed, expertise, and confidentiality, especially in high-stakes commercial and investment disputes. ISA is certainly prominent in Spain’s legal landscape when referring to international investors, but it is not the exclusive or always preferred method of resolving investment disputes.

For purely domestic investment disputes or where no arbitration clause exists, litigation is still widely used. Disputes involving administrative decisions, regulatory measures, or constitutional issues often go through Spanish courts.

The energy industry stands out far above the rest as the industry with more activity in recent years as the Spanish government, between 2010 and 2014, reversed or reduced subsidies and feed-in tariffs that had originally attracted foreign investment. These changes were perceived by many investors as a breach of legitimate expectations and the fair and equitable treatment (FET) standard under the ECT.

Other areas in which, to a much lesser extent, there have been investor–state claims in recent years are banking (eg, Antonio del Valle Ruiz and others v Spain, PCA Case No 2019-17) and mining (eg, Berkeley Exploration Ltd. v Spain, ICSID Case No ARB/24/22).

Spain’s ISA history is dominated by disputes under the ECT, particularly following its rollback of renewable energy incentives.

Below are some of the most legally significant cases, each shaping the interpretation of key principles like investment, FET standard and legitimate expectations.

• Charanne B.V. and Construction Investments v Spain (2015, SCC Case No V 062/2012). A Dutch investor challenged Spain’s 2010 regulatory changes to solar energy subsidies, claiming these reforms undermined their investment. Key legal issues: FET standard (Does it include the violation of investors’ legitimate expectations or not?) and the definition of investment (Does it include the shares and contractual rights or not?). Outcome: The tribunal rejected the claim, holding that Spain’s changes were not drastic enough to breach the FET standard. It emphasised that investors must anticipate some regulatory evolution.
• Novenergia II v Spain (2018, SCC Case No 2015/063). A Luxembourg-based fund invested in Spanish solar projects. Key legal issues: FET standard and legitimate expectations (whether or not Spain’s reversal of incentives was unforeseeable and disproportionate) and jurisdiction (as Spain argued that intra-EU disputes under the ECT were invalid post-Achmea). Outcome: The tribunal found Spain liable for breaching the FET standard and awarded EUR53 million. It rejected Spain’s jurisdictional objection, fuelling the intra-EU arbitration debate.
• Antin Infrastructure Services v Spain (2018, ICSID Case No ARB/13/31). Some UK investors in solar thermal plants claimed that Spain’s 2013–2014 reforms destroyed the economic viability of their projects. Key legal issues: FET standard and proportionality principle (whether or not Spain’s measures were excessive and discriminatory) and damages calculation (regarding loss of future income). Outcome: The tribunal awarded EUR112 million and reinforced the principle that radical regulatory shifts can breach the FET standard if they undermine investor confidence and stated that a proper approach for determining the amount of reparation is to assess the reduction of the fair market value of the claimants’ investment by determining the present value of cash flows claimed to have been lost.
• NextEra Energy Global Holdings B.V. and NextEra Energy Spain Holdings B.V. v Kingdom of Spain (2019, ICSID Case No ARB/14/11). Some Dutch companies (owned by a US one) invested in two solar thermal plants in Spain. Key legal issues: Jurisdiction and FET standard. Outcome: The tribunal awarded EUR290.6 million, one of the largest ISA awards against Spain, and stated that the representations and assurances of the Spanish authorities were the basis for a legitimate expectation that the economic regime would not be changed in a way that would undermine the security and viability of the investment. Regarding jurisdiction, the tribunal said that constitutional laws of the EU and its constant changes and interpretations by the CJEU are of no relevance and that the ECT’s genesis generates a presumption that it is not in contradiction with EU law and, consequently, it cannot retroactively construe Spain’s offer to arbitrate under the ECT as invalid.
• Green Power K/S and Obton A/S v Spain (2022, SCC Case No V 2016/135). Some Danish companies invested in the Spanish solar energy market and were affected by the regulatory measures adopted between 2010 and 2014. The claimants argue that these alterations violated Spain’s obligations under the ECT. Key legal issue: Jurisdiction. Outcome: The primacy of EU law precluded the unilateral offer to arbitrate in Article 26 of the ECT so that the tribunal had no jurisdiction to hear the claims brought by the claimants.
• Portigon AG v Kingdom of Spain (2025, ICSID case No ARB/17/15). A German financial institution financed three solar power plants in Spain. Key legal issue: Investment (whether or not debt instruments and financial arrangements – rather than equity ownership – qualified as “investments” under the ECT and ICSID Convention). Outcome: The tribunal affirmed jurisdiction, holding that project finance loans and hedging instruments can constitute protected investments under the ECT, but dismissed claimant claims.

These cases collectively shaped the global debate on regulatory risk, state sovereignty, and investor protection, and they continue to influence Spain’s legal and treaty strategy – including its withdrawal from the ECT.

Spain has taken a resistant and combative stance toward the enforcement of investor–state arbitration awards, particularly those rendered under the ECT. Spain has consistently filed appeals for annulment against condemnatory awards in intra-EU arbitrations under the ECT, arguing that they are invalid (citing the Achmea and Komstroy CJEU decisions), and has actively opposed enforcement efforts in multiple jurisdictions (including the US, UK, and Australia) invoking sovereign immunity under domestic laws (eg, the US Foreign Sovereign Immunities Act) to block recognition and execution of awards.

Specifically, Spain has sought the annulment of several awards such as the following.

• The Antin Infrastructure Services v Spain (ICSID Case No ARB/13/31) award. Spain alleged that the ICSID tribunal improperly conducted the proceedings and that it retained jurisdiction unlawfully. The ICSID ad hoc committee rejected Spain’s annulment application.
• The RREEF Infrastructure (G.P.) Limited and RREEF Pan-European Infrastructure Two Lux S.à r.l. v Kingdom of Spain (ICSID Case No ARB/13/30) award. Spain argued manifest excess of powers by the tribunal by improperly declaring its jurisdiction over an intra-EU dispute. Outcome: The ICSID ad hoc committee rejected the annulment application.
• The Foresight Luxembourg Solar 1 S.à r.l. and others v Kingdom of Spain (SCC Case No 2015/150) award. Spain requested the annulment of the arbitral award arguing that the award was invalid under Swedish arbitration law and EU law. Outcome: The Svea Court of Appeal declared the arbitral award invalid, citing incompatibility with EU law – particularly the lack of jurisdiction of arbitral tribunals to resolve disputes between EU member states and investors from other member states under the ECT.

Spain’s resistance strategy against awards’ enforcement efforts has had mixed success.

• Within the EU, enforcement is more complex due to CJEU rulings, but Spain’s blanket refusal to comply has drawn criticism from investors and legal scholars. Regarding the Antin Infrastructure Services v Spain case, the European Commission announced on 24 March 2025, that the arbitration award constitutes illegal state aid, meaning that if Spain pays the compensation recognised in the award, it will be in breach of EU regulations. Consequently, it orders Spain not to pay the amount recognised by the award and to ensure that there is no other payment, enforcement, or application of the arbitration award, either to Antin or to any other entity that has acquired or may acquire the rights derived from it (the decision in this case, which was handled as a pilot case, supports the position of Spain).
• Outside the EU, courts generally favour the enforcement of awards, rejecting Spain’s immunity and intra-EU objections.
1. The Federal Court of Australia has issued a ruling against Spain, ordering it to pay over EUR469 million, plus interest and legal costs, for four arbitration awards related to retroactive cuts to renewable energy subsidies (RREEF: EUR59.6 million; 9REN: EUR41.7 million; Watkins: EUR77 million; and NextEra: EUR290.6 million). The court dismissed Spain’s claim to sovereign immunity and rejected the European Commission’s intervention.
2. Spain paid, in June 2025, the EUR32 million compensation (EUR23.5 million plus interest) awarded by ICSID to Japan’s JGC in 2021 (JGC Holdings Corporation v Spain, ICSID Case No ARB/15/27). The award, whose rights belong to the US fund Blasket Renewable Investments, has been paid with the amounts that were deposited in Belgium in July 2024, after the seizure of the credit rights that Spain receives from the European Organization for the Safety of Air Navigation (Eurocontrol), via Enaire, by virtue of air traffic control fees, was authorised. The Spanish government proceeded with the payment of this compensation after receiving approval from the European Commission, which has confirmed that it does not constitute illegal state aid. This is the first time an award for cutting renewable energy subsidies has been completely enforced.

Spain has ratified a substantial number of bilateral agreements (BITs signed are over 90, with about 60 still in force). Partners include countries across:

• Latin America (Argentina, Colombia, Chile, Costa Rica, Dominican Republic, Cuba, El Salvador, Guatemala, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Peru, Uruguay, Trinidad and Tobago and Venezuela);
• Africa (Algeria, Egypt, Equatorial Guinea, Gabon, Libya, Mauritania, Morocco, Namibia, Nigeria, Senegal and Tunisia);
• Asia (China, Iran, Kazakhstan, Malaysia, Pakistan, Philippines, Tajikistan and Uzbekistan);
• Europe (Albania, Armenia, Azerbaijan, Belarus, Bosnia-Herzegovina, Georgia, Macedonia, Moldova, Russia, Serbia and Ukraine); and
• The Middle East (Saudi Arabia, Bahrein, Kuwait, Jordan, Syria and Lebanon).

Additionally, Spain is party to numerous multilateral agreements, primarily through its membership in the European Union (Spain benefits from all EU trade agreements, including those signed with Canada (CETA), Japan (EU–Japan EPA), South Korea, Mercosur (pending ratification), Vietnam, Singapore, and others), the World Trade Organization (WTO) and the Organisation for Economic Co-operation and Development (OECD).

It is highly likely Spain will continue ratifying new treaties, especially in the following areas.

• Post-ECT strategy – following its withdrawal from the ECT, Spain may seek new bilateral frameworks for investment protection in the field of energy.
• EU-led negotiations – Spain will likely ratify future EU agreements, such as EU–Mercosur (pending) EU–Australia (negotiations concluded) or EU–India (ongoing talks).
• Tax and digital economy treaties – Spain is expected to adopt more multilateral tax instruments and digital trade frameworks, especially those emerging from OECD and United Nations initiatives.

Spain’s BITs and its approach to multilateral investment treaties are broadly based on a model treaty framework, which has evolved over time. The most influential version was released in 2005, drawing from earlier OECD models and Spain’s own treaty practice.

The key and distinctive provisions typically found in Spain’s model BIT framework are as follows.

• FET standard:
1. It guarantees investors protection against arbitrary, discriminatory, or unreasonable state conduct.
2. It is often interpreted to include protection of legitimate expectations, especially regarding regulatory stability.

• National and most-favoured nation treatment (MFN):
1. This principle ensures foreign investors receive treatment no less favourable than domestic investors or those from third countries.
2. MFN clauses may extend procedural rights (eg, access to arbitration) from other treaties.

• Protection against expropriation – direct and indirect expropriation must be for a public purpose, non-discriminatory and accompanied by prompt, adequate, and effective compensation.
• Free transfer of funds – investors can freely transfer capital, profits, dividends, and other payments related to their investment, subject to limited exceptions (eg, bankruptcy or criminal enforcement).
• Full protection and security – it requires host states to provide physical and legal security to investments.
• Umbrella clause – it elevates contractual obligations between the state and the investor to treaty level, allowing breach of contract claims under the BIT.
• Investor–state dispute settlement (ISDS) – it offers access to international arbitration, typically ICSID or UNCITRAL, and often allows investors to choose between domestic courts and international arbitration.

Spain’s newer treaties and EU-led agreements include the following.

• Provisions on corporate social responsibility (CSR), labour rights, and environmental protection.
• Provisions on sustainable development (language promoting responsible investment aligned with climate and social goals).
• In EU treaties, traditional ISDS is being replaced by a standing tribunal and an appellate mechanism.

Spain is embedded in a broader free trade structure through its membership in the EU. This grants Spain access to a vast network of EU-negotiated free trade agreements (FTAs) and investment protection frameworks. As an EU member since 1986, Spain participates in all trade and investment agreements negotiated by the EU (as 2.1 Bilateral and Multilateral Investment Treaties shows).

These agreements offer market access, investment protection, and dispute resolution mechanisms for Spanish investors abroad and foreign investors in Spain. EU FTAs and investment treaties typically include the following.

• FET standard – it protects investors from arbitrary or discriminatory treatment.
• Protection against expropriation – it requires compensation if assets are seized.
• Free transfer of capital – it ensures investors can repatriate profits and funds.
• Transparency and CSR – newer treaties include provisions on labour rights, environmental standards, and corporate responsibility.

Spain’s treaties – especially those under the EU – are shifting toward modernised dispute resolution mechanisms.

• ISDS – still present in older BITs and some EU agreements, allowing investors to sue states directly.
• Investment court system (ICS) – a newer EU model replacing ISDS with a standing tribunal and an appellate body, aimed at increasing transparency and legitimacy.

Spain supports the EU’s push for a Multilateral Investment Court, which would standardise global investor–state dispute resolution. Spain’s withdrawal from the ECT signals a pivot toward EU-centric investment governance, emphasising sustainability and judicial reform. Spain will likely ratify upcoming EU agreements (eg, with Mercosur and Australia), expanding its trade and investment footprint.

Spain does not publish systematic commentaries on treaty provisions, official guidance documents for investors or arbitrators, or consolidated interpretive statements across its BIT network. This means interpretation often relies on tribunal jurisprudence, academic analysis, and comparative treaty review.

Spain has a national investment law framework, though it is not a single codified statute and it is composed of several legal instruments that regulate foreign investment, the most recent and central being Royal Decree 571/2023, of 4 July, on Foreign Investment. Spain aligns its national investment law with Regulation (EU) 2019/452, which sets a framework for screening foreign direct investment across the EU.

Foreign investment is generally liberalised in Spain, meaning investors can operate freely unless specific restrictions apply.

Royal Decree 571/2023 regulates the obligations to declare foreign investments in Spain for statistical purposes, which must be made after the closure of the transactions subject to declaration, and requires prior administrative authorisation for the closure – not the signing – of certain investment transactions in Spain, with both a general mechanism for investments in sensitive sectors such as critical infrastructure (energy, transport, water, health and communications) or media and technology affecting public order or security, and one specifically relating to activities directly related to national defence. Disputes over authorisation or compliance are handled through Spain’s administrative courts.

Spanish law does not provide for ISDS mechanisms so that investors must rely on domestic legal remedies unless protected by a treaty. Domestic law guarantees:

• protection against expropriation;
• principle of legality and publicity of norms;
• non-retroactivity of punitive provisions that are unfavourable or restrictive of individual rights;
• legal certainty; and
• prohibition of arbitrariness by public authorities.

Treaty protections often provide stronger guarantees. If foreign investors face discriminatory treatment or indirect expropriation, they may invoke treaty protections even if domestic remedies are limited.

Investor–state contracts are not typical or widespread in Spain in the way they might be in countries with less-developed legal systems or where foreign investment is heavily negotiated on a case-by-case basis. Spain generally relies on transparent legal frameworks, EU regulations, and bilateral/multilateral treaties to govern foreign investment – not bespoke contracts between the state and individual investors.

Works or service concession contracts that can channel foreign investment are usually administrative contracts subject to public law and disputes must be resolved in the contentious-administrative courts.

Some contracts entered into by public entities operating under private law or by private entities belonging to the public sector may allow arbitration (this depends on the nature of the contract and the contracting authority). Arbitration submission clauses may specify commercial arbitration forums (eg, ICC) rather than investment arbitration (eg, ICSID) and may be subject to Spanish administrative law, which can limit the scope of arbitration if the contract involves sovereign functions.

The most frequently cited complaints by investors (especially under the ECT because of Spain’s retroactive changes to its renewable energy incentive regime) are as follows.

• FET standard (the most invoked standard, by far) and particularly the frustration of investors’ legitimate expectations by dismantling a stable regulatory framework – notably the feed-in tariff system promised under Royal Decree 661/2007, and acting in a non-transparent and predictable manner.
• Indirect expropriation (less successful, but still frequently raised), because of Spain’s regulatory rollback that deprived investors of expected returns without formal nationalisation. Most tribunals have rejected expropriation claims, arguing that Spain’s actions were regulatory in nature and did not eliminate ownership rights.
• Breach of contract/umbrella clause, when investors had specific agreements or licences with the Spanish government. Some tribunals have treated regulatory decrees as general legislation, not binding contracts, unless specific commitments were made.

ISA typically arises under BITs or multilateral agreements like the ICSID Convention or UNCITRAL Rules, rather than under Spain’s domestic Arbitration Act (Law 60/2003). So, the limits on party autonomy are shaped by international frameworks, not Spanish law. Many BITs and other agreements contain specific clauses on arbitrator qualifications, nationality, and appointment procedures.

Spain has default procedures for arbitrator appointment under its Arbitration Act (Law 60/2003), which apply when the parties’ agreed method fails.

It is unlikely that this will happen. ISA typically follows international rules (eg, ICSID and UNCITRAL), not domestic Spanish law.

If Spanish law applies Article 15 of the Arbitration Act governs arbitrator appointment and if the parties’ method fails, either party may request the competent court (Civil and Criminal Chamber of the Superior Court of Justice) to appoint the arbitrator(s). The court ensures impartiality and independence, and its decision is final.

In multi-party cases, the Spanish Arbitration Act does not have a specific provision for joint appointment by multiple claimants or respondents. But courts and institutions may apply equitable solutions (if multiple parties cannot agree on a joint arbitrator, the court may appoint all arbitrators to ensure neutrality). Arbitral institutions (eg, Madrid Court of Arbitration and the ICC) often have internal rules for multi-party appointments (common list method or institutional appointment if consensus fails).

Most ISA involving Spain are governed by international treaties (eg, BITs, and the ICSID Convention), which have their own mechanisms for arbitrator appointment. In those cases, Spanish courts do not intervene in the selection process, and their role is limited to recognition and enforcement of awards, or procedural support (eg, interim measures).

Spanish courts have limited and highly circumscribed powers to intervene in the selection of arbitrators – and only if the arbitration is seated in Spain, and the parties have not agreed on a method for appointing arbitrators, or the agreed method provided for in the international rules fails or is obstructed. Spanish courts cannot intervene arbitrarily. Their powers are strictly procedural and limited to ensuring the appointment process is completed when the parties or institutions fail, verifying that arbitrators meet legal requirements (eg, independence or impartiality) and avoiding undue delay or obstruction of proceedings.

Spanish courts cannot override party autonomy or institutional rules (eg, ICSID or UNCITRAL rules) in arbitrations not seated in Spain, unless enforcement or recognition is involved. They cannot intervene in the merits of the dispute or tribunal composition once validly constituted.

The applicable challenge procedure often depends on the rules chosen by the parties, such as the ICSID Convention or the UNCITRAL Rules. Spanish courts do not intervene in these international mechanisms unless the arbitration is seated in Spain and domestic law applies.

The Spanish Arbitration Act contains provisions governing the challenge and removal of arbitrators, and these can apply in ISA if the arbitration is seated in Spain or Spanish procedural law is otherwise relevant.

Under Article 17 of the Arbitration Act, an arbitrator may be challenged on the following grounds.

• Lack of independence or impartiality.
• Failure to meet agreed qualifications.
• Incapacity or inability to perform duties.

A party must submit the challenge within 15 days of becoming aware of the grounds. The challenge is first decided by the arbitral tribunal itself (excluding the challenged arbitrator). If the tribunal rejects the challenge, the party may request the competent Spanish court to decide the matter.

The requirements for arbitrator independence, impartiality, and disclosure are foundational – and they are shaped both by Spanish national law and the rules of major arbitration institutions like ICSID and UNCITRAL.

In accordance with Spanish national law, arbitrators must be independent and impartial throughout the proceedings. These are mandatory requirements under Article 17 of the Arbitration Act. Arbitrators must disclose any circumstances that may give rise to justifiable doubts about their independence or impartiality. This includes prior relationships with parties or counsel, financial interests and affiliations with entities related to the dispute. Spanish courts have upheld these standards rigorously.

Under the ICSID Convention, Article 14 (1) requires arbitrators to be persons of high moral character, with recognised competence and independent judgment. Challenges can be made if a party believes the arbitrator lacks these qualities. ICSID tribunals have consistently emphasised manifest lack of independence or impartiality as grounds for disqualification.

Under UNCITRAL Arbitration Rules, Article 11 states that arbitrators must disclose any circumstances likely to give rise to justifiable doubts about their impartiality or independence. A party may challenge an arbitrator if such doubts exist. Arbitrators must update parties if new conflicts arise during proceedings.

Failure to disclose relevant ties – even if they seem minor – can lead to challenges or annulment of awards. Even the appearance of bias can be enough to trigger a valid challenge. Many arbitrators follow the IBA Guidelines on Conflicts of Interest, which offer a structured approach to disclosure and challenge.

In ISA seated in Spain, an arbitral tribunal is permitted to award preliminary or interim relief, and such relief is binding under Spanish law.

Under Article 23 of the Spanish Arbitration Act (Law 60/2003) arbitral tribunals may grant interim measures to preserve rights, prevent harm, or ensure the effectiveness of the final award. These measures are binding on the parties once granted. However, tribunals lack enforcement power – so parties may need to seek judicial assistance to enforce the relief.

Spanish courts are empowered to support arbitration by enforcing interim measures, as clarified in Article 8.3 and 11.3 of the same Act.

There is no exhaustive list, but common types of relief include:

• freezing orders (eg, provisional attachment of assets);
• orders to preserve evidence;
• injunctions to prevent harmful actions;
• security for costs; and
• status quo preservation (eg, halting contract termination or asset transfer).

Spanish courts apply principles like fumus boni iuris (appearance of good law) and periculum in mora (risk that the award may be ineffective due to the length of the proceeding) when deciding whether to enforce such measures.

If the arbitration is governed by ICSID or UNCITRAL rules, ICSID tribunals can order binding interim measures under Article 47 of the ICSID Convention and UNCITRAL tribunals may grant interim relief under Article 26 of the UNCITRAL Arbitration Rules. Courts at the Spanish seat may assist in enforcement.

Spanish law does not restrict the tribunal’s power to award interim relief in investor–state cases, provided the arbitration is seated in Spain or Spanish courts are involved in enforcement.

In investor–state arbitration, Spanish courts play a supportive but limited role when it comes to interim or preliminary relief. Their involvement depends on whether or not the arbitration is seated in Spain and whether or not the parties or tribunal require judicial assistance to enforce or secure such relief.

Under Article 11.3 of Spain’s Arbitration Act (Law 60/2003), parties may request interim measures from Spanish courts before the arbitration begins or during the arbitration proceedings. Spanish law recognises that arbitral tribunals and courts have concurrent powers to grant interim relief. However, tribunals cannot enforce their own interim orders without court assistance – especially if third parties or sovereign assets are involved.

Spanish courts do not interfere with the merits of the arbitration, and their role is limited to procedural support, such as enforcing interim measures.

In ICSID or UNCITRAL arbitrations, ICSID tribunals can order binding interim measures under Article 47, but enforcement may require domestic court action if assets in Spain are involved. UNCITRAL tribunals rely on the seat of arbitration for enforcement – so if Spain is the seat, Spanish courts may be asked to enforce interim orders.

Under the Spanish Arbitration Act (Law 60/2003) arbitral tribunals have the power to grant interim measures, which may include security for costs. This power is recognised under Article 23, which allows tribunals to adopt any interim measure they deem necessary.

Spanish Law permits third-party funding (TPF) of investor–state arbitration claims (although it is not specifically regulated, it is permitted under general principles of civil and commercial law as the Spanish Civil Code allows for the transfer of credit rights, which includes the right to proceeds from legal claims), and while it is not yet widespread, it is gaining traction, especially in high-stakes disputes involving energy and infrastructure.

As of 2025, 16% of ICSID cases globally involve TPF – a figure that includes claims against Spain. The rise in unpaid awards and costly litigation has made Spain a hotspot for funders, especially in cases where investors seek compensation for regulatory changes in renewable energy.

In Spain, there is no specific regulatory framework governing TPF, which is covered by the principle of freedom of contract and freedom of agreement under Article 1255 of the Civil Code (Supreme Court Judgment, Contentious-Administrative Chamber, 53/2020, of 22 January 2020).

Spanish Supreme Court jurisprudence has affirmed the legality of transferring credit rights, which includes rights to proceeds from legal claims. This forms the legal backbone for TPF arrangements under Article 1526 et seq of the Spanish Civil Code.

Although no landmark Supreme Court case has directly ruled on the full scope of TPF in ISA, the Court has recognised the validity of funding contracts as long as they respect public policy and professional ethics and emphasised the importance of transparency and disclosure, especially when funders may influence litigation strategy.

Spain has emerging rules and practices requiring the disclosure of TPF in arbitration, particularly through institutional rules, and tribunals are increasingly factoring TPF into decisions on security for costs – though cautiously.

While Spanish law does not mandate disclosure by statute, arbitral institutions in Spain do. The Spanish Court of Arbitration and the Madrid International Arbitration Centre (CIAM) require parties to disclose the existence and identity of TPF to prevent conflicts of interest between arbitrators and funders, promote transparency and procedural fairness and ensure informed decision-making on costs and interim measures.

Additionally, Spain’s legal community is watching closely as the European Parliament pushes for a directive that would regulate TPF across member states, including mandatory disclosure and limits on funder influence and remuneration.

Spanish tribunals and courts do not automatically grant security for costs just because TPF is involved. Instead, they apply a case-by-case analysis, considering financial standing of the claimant, risk of non-payment of adverse costs, whether or not the funder has explicitly committed to cover costs, and the evidence of bad faith or procedural abuse. In practice tribunals may request disclosure of the funding agreement to assess the funder’s obligations and remain reluctant to penalise funded claimants, unless there is a real risk that the respondent will be unable to recover costs if it prevails.

Spanish law itself does not impose specific requirements regarding the notice of dispute or consultation period. Instead, these pre-arbitration procedural requirements are typically governed by the applicable investment treaty (eg, BIT or EU agreement), the arbitration rules chosen (eg, ICSID or UNCITRAL) and/or any contractual provisions between the investor and the Spanish state or state-owned entity.

Most BITs signed by Spain include pre-arbitration steps, such as notices of dispute, cooling-off periods and/or exhaustion of local remedies (though many modern BITs waive this last requirement).

Balancing confidentiality with transparency in investor–state arbitration under Spanish law is a nuanced challenge – especially when public funds, regulatory decisions, or environmental impacts are involved.

Under the Spanish Arbitration Act (Law 60/2003) arbitration is generally private and confidential, unless parties agree otherwise. There is no statutory obligation for transparency in investor–state disputes seated in Spain. However, public entities (like the Spanish government or state-owned companies) may be subject to administrative transparency laws, such as the Ley de Transparencia, acceso a la información pública y buen gobierno (Law 19/2013), which requires disclosure of public spending and decisions. So, while the arbitration itself may be private, public accountability laws can compel disclosure of certain aspects – especially if awards affect the state budget or regulatory frameworks.

Spain is party to numerous BITs and EU treaties, and many of these encourage or require publication of awards, allow third-party participation (amicus curiae) and promote open hearings in certain cases. For example, UNCITRAL’s Transparency Rules (2014) apply automatically to treaties signed after April 2014 and can be adopted voluntarily in older treaties. These rules promote public access to documents, open hearings and disclosure of tribunal composition and funding.

Spain’s evolving treaty practice increasingly reflects these norms, especially in light of EU-wide reforms to ISDS.

Spanish law imposes limits on the types of remedies that an arbitral tribunal may award – especially in investor–state arbitration or international arbitration seated in Spain. These limits are shaped by the Spanish Arbitration Act (Law 60/2003), Spain’s civil law tradition, and public policy considerations.

• Punitive damages are not permitted. Spain follows a civil law system, which does not recognise punitive damages. Enforcement of awards that include punitive damages may be refused in Spain on public policy grounds, especially under the New York Convention or Spanish enforcement rules. Spanish courts apply a triple test of legitimacy to assess whether a foreign award with punitive elements violates Spanish public order.
• Rectification and specific performance are permitted. Tribunals may order contractual rectification, restitution, or specific performance, provided the remedy is legally available under the applicable law and it does not infringe sovereign powers or administrative prerogatives of the Spanish state.
• Injunctions and interim measures are permitted with limits. Arbitral tribunals seated in Spain may grant interim relief, including injunctions, under Article 23 of the Arbitration Act. However, enforcement of such measures often requires judicial assistance, especially if they affect third parties or public entities.
• Declaratory relief is permitted. Tribunals may issue declarations of rights or obligations, which are common in investor–state disputes (eg, breach of treaty, or unlawful expropriation).

Spanish courts may refuse to enforce arbitral awards if the remedy violates Spanish public order, conflicts with mandatory legal norms or infringes on constitutional principles, such as proportionality or due process.

In Spanish law – especially in arbitration – valuation methodologies for quantifying damages are not rigidly prescribed, but tribunals and courts tend to rely on internationally accepted financial approaches, tailored to the nature of the claim and the available evidence.

The most common valuation methodologies in Spanish legal practice are the following.

• Discounted cash flow (DCF) – most used in cases involving business interruption, expropriation, or loss of future profits. Spanish courts and arbitral tribunals accept DCF if projections are reliable, but they scrutinise assumptions rigorously. It is often challenged if the business lacks a track record or if future cash flows are speculative.
• Market value/comparable transactions – used in shareholder disputes, M&A litigation, or investment treaty arbitration. Spanish tribunals may prefer this method when objective market data is available, and the asset is actively traded.
• Cost-based/replacement cost – applied in construction disputes, property damage, or asset valuation. It is often used when income-based valuation is not feasible, such as for infrastructure or machinery.
• Book value/net asset value – sometimes used in corporate disputes or insolvency-related claims.
• Liquidation value – relevant in bankruptcy proceedings or when a business is no longer a going concern.

Spanish courts and arbitral tribunals require causation between the wrongful act and the loss, foreseeability and certainty of damages and expert evidence, often from forensic accountants or valuation specialists.

In investor–state arbitration involving Spain, parties are generally entitled to seek interest, legal and expert fees, and arbitral institution costs – but the awarding of these items depends on several factors, including the arbitration rules, the investment treaty, and the tribunal’s decision.

The Spanish Arbitration Act (Law 60/2003) does not prescribe a fixed rule for cost allocation and tribunals have broad discretion to allocate costs “as they deem appropriate”.

Under Spanish law and international investment arbitration principles, an investor has a duty to mitigate its losses. This duty is not always explicitly stated in treaties, but it is widely recognised by arbitral tribunals and rooted in general principles of law – including those applicable in Spain.

Spanish civil law incorporates the principle that a party must act reasonably to limit its damages. This is aligned with good faith obligations under the Spanish Civil Code, which influence contractual and tort-based claims. If an investor fails to take reasonable steps to reduce its losses, compensation may be reduced or denied.

Tribunals often apply Article 39 of the ILC Articles on State Responsibility, which states that compensation should be adjusted if the injured party contributed to its own loss. This includes contributory fault (eg, negligent conduct) and failure to mitigate (eg, ignoring opportunities to reduce harm).

Spain follows a structured and internationally aligned approach to enforcing arbitral awards, shaped by its domestic law, treaty obligations, and public international law principles.

Spain is a party to both the ICSID Convention and the New York Convention, which govern the enforcement of investor–state awards depending on the arbitration forum.

• ICSID Awards – under Article 54 of the ICSID Convention, Spain must recognise and enforce ICSID awards as if they were final judgments of its own courts. The enforcement is automatic, subject only to procedural formalities and no review of the merits or jurisdiction is permitted.
• Non-ICSID Awards (eg, UNCITRAL) – enforcement is governed by the New York Convention and Spain’s Civil Procedure Act and Spanish courts may refuse enforcement on limited grounds:
1. lack of valid arbitration agreement;
2. violation of due process;
3. award exceeding scope of submission;
4. award is not yet binding or has been set aside; or
5. enforcement would violate Spanish public policy.

If an award is annulled by courts at the seat, Spanish courts will typically refuse enforcement, especially under the New York Convention (Article V (1)(e)). However, for ICSID awards, annulment must occur through ICSID’s own internal process – not national courts. Spanish courts do not enforce ICSID awards annulled by ICSID ad hoc committees, but they do not defer to annulments by domestic courts outside ICSID.

When an award is under challenge, but not yet annulled, Spanish courts may suspend enforcement proceedings pending resolution at the seat or proceed with enforcement if the challenge appears frivolous or unlikely to succeed (this is a discretionary decision, and courts weigh the strength of the challenge, the urgency of enforcement and the potential prejudice to the parties).

Spain, like other states, may invoke sovereign immunity at the enforcement stage – but with limited success as under Spanish law and international practice waiver of immunity is implied when a state consents to arbitration and Spanish courts follow the principle that jurisdictional immunity is waived by treaty-based arbitration clauses. However, execution immunity (eg, seizure of state assets) may still apply, especially for non-commercial assets like embassies or central bank reserves.

Recent cases in UK, US, and EU courts have rejected Spain’s immunity claims in enforcement of ICSID awards, affirming that Article 54 of the ICSID Convention constitutes a waiver of immunity.

Spanish courts adopt a generally pro-enforcement stance toward arbitral awards, especially under the framework of the New York Convention and the ICSID Convention, to which Spain is a party. However, there are nuanced standards and exceptions – particularly around public policy and sovereign immunity – that shape enforcement outcomes.

Spanish courts typically favour enforcement unless there is a clear and compelling reason to refuse it. Spanish courts distinguish between the following.

• Domestic public policy – this refers to fundamental principles of Spanish law, such as due process, legality, and non-discrimination. Enforcement may be refused if the award violates these principles in a manifest and serious way.
• International public policy – this is a broader and more flexible category, encompassing Spain’s obligations under international law, including human rights and treaty commitments. Spanish courts tend to apply international public policy when assessing foreign awards, especially in investor–state disputes.

The violation must be “manifest, serious and intolerable” to justify refusal. Minor procedural irregularities or controversial findings are not sufficient.

Spanish courts recognise two types of immunity.

• Jurisdictional immunity – this is generally waived when a state consents to arbitration. Spanish courts follow the principle that consent to arbitration implies waiver of jurisdictional immunity, especially in treaty-based investor–state disputes.
• Execution immunity – this is more robust and harder to overcome. Spanish courts protect non-commercial assets (eg, embassies, military property, and central bank reserves) but commercial assets may be subject to enforcement if the state has waived immunity or acted in a commercial capacity.

Spain has resisted enforcement of several ICSID awards by invoking execution immunity, but courts in other jurisdictions (the UK, US and Australia) have increasingly rejected these defences.

Spanish courts can enforce foreign arbitral awards under the New York Convention or ICSID Convention, but enforcement against foreign assets located in Spain depends on several factors.

• If the assets belong to a foreign state, Spanish courts recognise sovereign immunity from execution for non-commercial assets (eg, embassies, and military property). Commercial assets (used in trade or business) may be subject to enforcement if the foreign state has waived immunity or acted in a commercial capacity. Spanish courts apply a restrictive theory of sovereign immunity, meaning immunity does not apply to commercial activities. However, enforcement is still subject to judicial decision and public policy considerations.
• When enforcing awards abroad against Spanish state assets, the approach depends on the jurisdiction. Most jurisdictions (eg, the UK, US and France) apply restrictive immunity, allowing enforcement against commercial assets (bank accounts held by Spanish government or agencies, real estate not used for diplomatic purposes, receivables from commercial contracts, and state-owned companies operating abroad). Spain has attempted to resist enforcement by invoking execution immunity, especially in cases involving Antin, NextEra, and CSP Equity. Courts abroad may allow discovery proceedings to trace Spanish assets, especially in common law jurisdictions.

Spanish courts – and many foreign courts – will pierce the corporate veil only in exceptional cases, such as fraud or abuse of legal personality, asset shielding to avoid enforcement, and economic unity between the state and its corporate vehicle. In Spain, the doctrine is grounded in civil law principles (good faith, and prohibition of abuse).