
On Wednesday, at the NATO summit in The Hague, Spanish Prime Minister Pedro Sánchez formally rejected the alliance’s newly agreed aspirational guideline for member states to increase defense spending to 5% of national GDP by 2035. In a carefully negotiated compromise, NATO permitted Spain to endorse the summit’s joint communiqué with a subtle but significant textual modification: while “allies commit” to the target, Spain was recognized as having “a different path.” This makes Spain the only member state to secure a formal exemption an unusual divergence in NATO’s history of collective consensus.
This development comes amid rising geopolitical tensions on NATO’s eastern flank, particularly regarding Russian activity in Ukraine, Belarus, and the Baltic region. Poland and Belgium, among others, criticized Spain’s position as undermining NATO’s collective credibility. US President Donald Trump, speaking in a private capacity, criticized Spain’s decision and suggested economic retaliation, though no such policy has been adopted by the U.S. administration.
Yet from a legal standpoint, Spain has not violated any treaty obligation. The North Atlantic Treaty (1949), which governs NATO, does not require members to commit a fixed percentage of GDP to defense. Article 3 of the Treaty states that parties will “maintain and develop their individual and collective capacity to resist armed attack” but leaves implementation entirely to national discretion. No binding protocol, annex, or amendment to the North Atlantic Treaty mandates a specific GDP-based threshold for defense spending. The 2% GDP guideline, first proposed at the 2006 Riga Summit and reaffirmed in the 2014 Wales Summit Declaration, has always been a political, not legal, benchmark. The proposed 5% goal, introduced at the 2025 summit, follows this same soft-law trajectory, lacking treaty status or enforceable obligations.
Spain’s refusal thus raises pressing questions about the nature of legal obligations in multilateral security treaties. Can repeated political declarations amount to customary international law? Can reputational pressure substitute for legal enforceability? And what happens when a major Western European member overtly refuses to follow an alliance-wide strategic norm?
This incident reflects a deeper structural issue in NATO’s legal fabric: the tension between the alliance’s political unity and the legal autonomy of its members. NATO operates by consensus an institutional practice rather than a codified voting rule and every member, including Spain, effectively holds veto power over final communiqués. That Spain was permitted to remain “in” the consensus while standing “outside” the main commitment signals a shift in how NATO handles internal dissent.
Interestingly, Spain’s invocation of sovereignty and social priorities echoes its historic ambivalence toward military expansion. In 1986, a nationwide referendum conditionally affirmed Spain’s NATO membership on the understanding that no nuclear weapons would be stationed on Spanish territory and that Spain would maintain a reduced level of integration into NATO’s military structure. While those conditions were political and not formally codified in international law, they continue to reflect Spanish public sentiment. Prime Minister Sánchez and Economy Minister Carlos Cuerpo have insisted that Spain’s 2.1% GDP defense goal is consistent with its obligations and necessary to safeguard EU-aligned investments in welfare, green infrastructure, and education.
Comparatively, other NATO members including Canada, Germany (prior to 2022), Belgium and Luxembourg have routinely failed to meet defense spending targets without facing legal sanction. NATO’s annual reports and summit declarations demonstrate that these benchmarks are enforced through political and reputational means rather than legal instruments. Spain’s open divergence from a high-profile strategic goal may mark a new phase: the normalization of selective opt-outs, justified not by incapacity but by deliberate national policy.
From a legal perspective, Spain’s stance reinforces the elasticity of treaty-based defense commitments. The Vienna Convention on the Law of Treaties (1969) codifies the principle of pacta sunt servanda that treaties in force must be performed in good faith but this principle applies only to obligations that are binding under international law. Spain’s negotiated exemption does not violate any NATO treaty provision, nor does the 5% target meet the threshold of opinio juris required to evolve into customary international law. As Prosper Weil noted in his seminal critique of “relative normativity,” soft law norms often lack the legal determinacy required to bind states.
Nevertheless, the strategic consequences are harder to contain. NATO risks evolving into a “tiered alliance,” where some states (notably Poland, the U.S., and the Baltic nations) shoulder the rising burden of deterrence while others leverage opt-outs to prioritize domestic spending. This divergence may erode the sense of mutual risk and collective sacrifice that underpins the credibility of Article 5, the alliance’s collective defense clause.
As a law student observing these developments from within Europe, I see this not as a betrayal, but as a wake-up call. Spain’s position is legally valid and democratically accountable, but it should provoke NATO to reexamine how it communicates and codifies its strategic expectations. Should such commitments remain soft law? Is it time for NATO to renegotiate its core treaty framework to reflect the shifting threat environment and fiscal constraints of its members?
In the absence of reform, the alliance may continue to rely on a patchwork of political goodwill rather than legal clarity. Spain’s exemption, though procedurally negotiated, risks becoming a precedent for further fragmentation and with it, the gradual weakening of NATO’s collective security architecture.