The Phenomenon of Parallel Litigation: Foundations and Implications in Cross-Border Dispute Resolution

Introduction
Differences in international jurisdictional rules among states often result in multiple courts in different countries asserting jurisdiction over the same international dispute. For various reasons, more than one court may proceed with the same or related cases, giving rise to parallel litigation and its accompanying adverse effects. Although some legal systems, despite possessing international jurisdictional rules, have not established effective mechanisms to address parallel litigation, Iranian law presents a distinct stance. Article 971 of the Iranian Civil Code (1928) obliges Iranian courts to continue hearing a case even where the same dispute has already been filed and is pending before a foreign court. This article aims to provide a precise introduction to parallel litigation and to raise awareness among Iranian legislators regarding the approach enshrined in Article 971 of the Civil Code.
 
Methods
This study adopts a descriptive-analytical methodology without limiting its analysis to a single legal system. In clarifying key concepts and examining the causes and adverse effects of parallel litigation, reference is made to legal doctrines from various jurisdictions. Particular attention is devoted to Iranian law, both in the conceptual discussion and in the presentation of findings, in order to offer a concise assessment of the strengths and weaknesses of the Iranian legal framework in addressing parallel proceedings. The research is based on a library-oriented method of data collection.
 
Results and Discussion
Parallel litigation in international disputes occurs when identical or related claims are simultaneously brought before the courts of two or more states. Typically, the presence of the same parties, subject matter, and cause of action renders two claims legally identical. Where claims are so closely connected that failing to adjudicate them before a single forum risks the issuance of conflicting judgments, they are regarded as related. The phenomenon of parallel litigation arises when three conditions are met: first, the courts of at least two jurisdictions must possess concurrent jurisdiction over the dispute. If one court holds exclusive jurisdiction, parallel proceedings are generally precluded. Second, the same or closely related claims must be instituted before different national courts. Third, both courts must proceed with adjudication concurrently. When these criteria are fulfilled, the potential for procedural inefficiency and inconsistent outcomes becomes a central concern in transnational litigation.
The unilateral character of international jurisdictional rules, coupled with the absence of a supranational authority to allocate jurisdiction among states and the lack of a comprehensive international instrument prescribing uniform criteria for the determination of jurisdiction, constitutes a major cause of parallel litigation in private international law. Furthermore, the complex interaction between international jurisdiction and the applicable substantive law, along with significant differences in resulting judgments across national legal systems, further increases the risk of concurrent proceedings. In addition, the strategic use of procedural mechanisms by a party acting in bad faith is often an important factor in generating parallel litigation.
Parallel litigation leads to several negative consequences. One major effect is the increased cost of litigation for the parties involved in international disputes. It also causes courts in different countries to expend time and resources on the same case, even though one of the resulting judgments may ultimately not be recognized or enforced. Parallel proceedings also raise the risk of conflicting decisions, which can result in a denial of justice and may even contravene the public policy of one of the states involved. Furthermore, such litigation may be seen as inconsistent with international comity and can potentially harm the political relations between the states handling the case.
 
Conclusions
The adverse effects of parallel litigation have prompted many legal systems to adopt serious measures and implement various mechanisms to address the issue. Under Iranian law, although the jurisdiction of Iranian courts may be excluded through choice of court agreements, the current lack of attention to the problem of parallel litigation remains problematic. It is therefore recommended that Article 971 of the Civil Code be amended. Specifically, Iranian courts should be permitted to stay proceedings where the same case has already been brought before a foreign court. Furthermore, if a recognizable and enforceable foreign judgment is rendered, the claim should be dismissed.