Jurisdiction and enforcement of foreign judgments are separate issues in private international law. When arising outside of the context of international conventions, they are not necessarily related.
In principle, there is no obligation to enforce foreign judgments on the ground that, if the case had been litigated in the forum, the forum would have retained jurisdiction. Many states apply the same jurisdictional rules to assess whether to retain jurisdiction or to enforce a foreign judgment, but they have no obligation to do so, and many states assess the jurisdiction of foreign courts on a different basis.
The situation might be different in the context of an international convention. This is because the convention has established obligations as between the contracting states.
Where a convention contains both rules of international jurisdiction and recognition of foreign judgments, the issue does not arise. But many conventions only include one category of rules. They provide rules of international jurisdiction but are silent on the enforcement of the resulting judgments or, conversely, only provide rules of recognition and enforcement of foreign judgments (as, for instance, the 2019 Hague Judgments Convention).
Where a convention only contains rules of international jurisdiction, should it be considered that contracting states are under no obligation to enforce a judgment rendered by another contracting state on the basis of such rules? That would be quite problematic if the relevant rules of jurisdiction were both exclusive and narrow. A contracting state which would not enforce a foreign judgment might not have jurisdiction under the relevant convention to retain jurisdiction.
There are quite a few of such conventions in the field of international carriage. They include, for instance, the 1929 Warsaw and the 1999 Montreal Conventions for the Unification of Certain Rules Relating to International Carriage by Air.
In Rothmans v. Saudi Arabian Airlines, Mustill J. (as he was then) once gave his view on the reason why these conventions do not include rules on enforcement of judgements. He held:
International conventions of this kind tend to prescribe jurisdiction in narrow terms, on the assumption that the case where the defendant has insufficient assets to satisfy the claims in any of the stipulated countries is catered for by the ready availability of enforcement in other countries which is available via the various conventions on mutual recognition of judgments.
With all due respect, however, it is unclear to which “various conventions on mutual recognition of judgments” the distinguished judge was referring to.
A major issue for interpreting jurisdictional rules contained in international conventions as entailing obligations to enforce the resulting judgments is the strict rules of interpretation of treaties under the Vienna Convention on the Law of Treaties. But many of these private law treaties contain their own provisions on interpretation, which certainly derogate from the Vienna Convention.
The issue also arises in the context of the 2001 Cape Town Convention, which contains rules of international jurisdiction, but no rule of enforcement of judgments. In a recent article on Enforcement of Court Decisions Under the Cape Town Convention, I argue that the jurisdictional rules of the Convention should be considered as entailing rules on the enforcement of foreign judgments, and explore what these implicit rules could be.
The abstract of the article reads:
The purpose of this article is to explore the influence of the Cape Town Convention on the enforcement of foreign judgments. Although the issue is not expressly addressed by the Convention, the article argues that the jurisdictional rules of the Convention should be interpreted as entailing an implicit obligation to enforce the resulting judgments. After demonstrating that such conclusion would be consistent with the rules of interpretation of the Convention, the article explains what the regime of the implicit obligation to enforce judgments made under the Convention would be.