The determination of the law governing international arbitration agreements constitutes one of the most controversial and complex issues in contemporary arbitration law. This issue directly affects the validity, enforceability, and overall effectiveness of arbitration as a dispute resolution mechanism. In practice, arbitration agreements are typically incorporated as clauses within the underlying or main contract, which raises the fundamental question of whether the law governing the main contract necessarily extends to the arbitration agreement, or whether the latter may be subject to a distinct and independent legal regime. The absence of a clear consensus in comparative law and international arbitral practice has resulted in legal uncertainty and increased practical risks for contracting parties.

This article addresses this problem by examining, from a comparative perspective, the possibility of subjecting the international arbitration agreement to a law different from that governing the main contract, and by ultimately analysing the position of Iranian law within this framework. The central research question is whether, by relying on the principle of separability of the arbitration agreement or through the application of the doctrine of dépeçage, it is possible to determine a distinct governing law for the arbitration agreement, or whether, in the absence of an express choice of law by the parties, the arbitration agreement must be governed by the same law as the main contract.

The importance of this issue is amplified by the fact that the law governing the arbitration agreement has a direct impact on critical matters such as the substantive validity of the arbitration clause, the parties’ capacity, interpretation of the agreement, transferability, waiver of the right to arbitrate, and ultimately the recognition and enforcement of arbitral awards. An incorrect approach to this question may lead to the invalidity of the arbitration agreement or the ineffectiveness of the entire arbitral process, outcomes that are fundamentally incompatible with the core objectives of international commercial arbitration, namely efficiency, expediency, and finality in dispute resolution.

The methodology adopted in this article is descriptive–analytical and based on library research. The study relies on a comparative analysis of international arbitration instruments (including the 1958 New York Convention, the Geneva Convention, and the European Convention on International Commercial Arbitration), leading national arbitration laws (notably those of France, Switzerland, the United States, and England), landmark arbitral and judicial decisions, and scholarly doctrine. Within this framework, the principle of separability of the arbitration agreement, its dual contractual and procedural nature, and the scope and limits of the doctrine of dépeçage are examined independently and in detail.

The findings of the research demonstrate that although the principle of separability of the arbitration agreement is widely accepted in international arbitration law, it does not imply the absolute and comprehensive independence of the arbitration agreement from the main contract. Rather, this principle merely ensures that the invalidity or termination of the main contract does not automatically render the arbitration agreement invalid. It does not, however, mandate that the arbitration agreement must, for all purposes—particularly with respect to the determination of the governing law—be subject to a different legal system. Furthermore, the analysis reveals that treating the arbitration agreement as a fully autonomous contract for the purpose of determining its governing law faces serious theoretical difficulties and may lead to unpredictable and inconsistent outcomes.

With regard to the doctrine of dépeçage, the article shows that while voluntary dépeçage—arising from the parties’ express or clearly implied choice—may provide a legitimate basis for applying a different law to the arbitration agreement, objective or involuntary dépeçage is difficult to justify, except in exceptional and narrowly defined circumstances, due to its adverse impact on legal certainty. In particular, where the parties have expressly chosen the law governing the main contract, resorting to objective dépeçage in order to detach the arbitration agreement from that law lacks strong theoretical and practical justification.

In its final part, the article focuses on Iranian law and demonstrates that although the Iranian Law on International Commercial Arbitration and certain international arbitration instruments recognised within the Iranian legal system acknowledge the separability and independence of the arbitration agreement, this recognition does not amount to acceptance of the application of a different substantive law to the arbitration agreement. Based on an analysis of the relevant statutory provisions, existing practice, and underlying legal principles, the article concludes that, in the absence of an express choice of law governing the arbitration agreement, Iranian law subjects the arbitration agreement to the law governing the main contract, and that the doctrine of dépeçage does not, in practice, provide a reliable basis for the application of a different governing law.

The article concludes that the unconditional acceptance of the independence of the law governing the arbitration agreement is not only inconsistent with the logic of contract law but may also undermine predictability and legal certainty in international arbitration. A coherent and reasonable approach is to presume that the law governing the arbitration agreement follows the law governing the main contract, unless the parties have clearly and demonstrably expressed a contrary intention.