Two tenets are central to the Common Law rules for enforcement and recognition of foreign judgments. The first is that, subject to public policy, the enforcing court does not review the substance of the decision; in other words, mistake is no defence. The second is that, apart from ensuring that the judgment was not obtained by fraud or through a breach of the requirements of natural justice, the prime consideration for enforcement is whether the foreign court was competent to issue the judgment; in other words, whether it had jurisdiction.
These two tenets are eminently reasonable. A foreign judgment is after all both a judgment—like a local judgment, and foreign—like a right acquired under a foreign law. The validity of local judgments and of foreign unadjudicated rights depends on jurisdiction: local judgments depend on adjudicatory jurisdiction (often defined in the rules of service); foreign rights—on legislative or prescriptive jurisdiction (the jurisdiction of a system to regulate the situation substantively, as defined in choice-of-law rules). It thus seems appropriate to require jurisdiction of foreign judgments too. Local judgments, once final, are never subject to review, and can be attacked on the grounds that they were obtained by fraud only exceptionally. Rights acquired under a foreign law cannot be refused enforcement because of their substance and are subject only to the public policy exception. It thus seems appropriate to immunise foreign judgments from substantive review too. Foreign judgments—adjudicated rights—are of course different from foreign unadjudicated rights in that they are the product of a process. So, as in the case of local judgments, it should nonetheless be possible, in limited circumstances, to examine whether the process was tainted by fraud. So too, they differ from local judgments in that the process from which they emerge is not a local one; it cannot be relied upon in the same way as locally controlled and institutionalised procedures. It thus seems reasonable that, while prevented from reviewing the substance of a foreign decision, the court should be permitted to require of it a minimal level of procedural justice.