US Civil Litigation : Enforcing a UK Judgment in the US

There is no international treaty in force between the United States and any other country on reciprocal recognition and enforcement of judgments. The extent to which the U.S, or any state, recognises the judgments of foreign nations is, in the absence of relevant state law, a matter of choice governed by the principle of “comity."

Comity is considered to be neither a matter of absolute obligation, nor of mere courtesy and good will. U.S. courts will generally recognise foreign judgments and decrees unless enforcement would be prejudicial or contrary to fundamental notions of what is decent and just.