Court's use of foreign law
At the Volokh Conspiracy, Jim Lindgren has a post regarding Justice Ginsburg's references to foreign law, linking to an interesting study on use of foreign law by the Supremes. The gist of the study is that:
1. References to foreign law by the Court go far back into the early republic;
2. The references in constitutional cases have, however, recently escalated.
3. The practice may be justifiable when a constitutional provision refers to reasonableness or its like (cruel and unusual punishment springs to mind) but is hard to justify when construing an express American right or power that lacks such wording. That is, in the great majority of constitutional law cases.
4. In those cases, reference to international standards is suggestive that members of the Court are reaching out to justify illegitimate policy-making, making law and policy rather than construing it.
[Update: Haven't had time to read the study, so I don't know if it counts British common law decisions. The summary refers to an 1820 decision on the definition of piracy. I can readily see use of foreign law in that context, since piracy is an international crime defined largely by international tradition -- that is, a sort of international common law.]