A lot of VC readers are familiar with the debate over the use of foreign law to interpret the Bill of Rights. It's interesting that most discussions of this issue (not all, but most) overlook a prominent historical example: the use of the exclusionary rule for state violations of the Fourth Amendment, in which foreign law played a role in initially leading the Supreme Court to reject the use of the exclusionary rule under the Due Process clause.

  The key case is Wolf v. Colorado, 338 U.S. 25 (1949), which held that the Fourth Amendment was applicable to the states through the Due Process clause but that its exclusionary rule was not. Doctrinally speaking, the question was whether the exclusionary remedy was "implicit in the concept of ordered liberty" such that it was required under the Due Process clause to be applicable to the states. Justice Frankfurter ruled that it was not, based in part on international practice:

[T]he immediate question is whether the basic right to protection against arbitrary intrusion by the police demands the exclusion of logically relevant evidence obtained by an unreasonable search and seizure because, in a federal prosecution for a federal crime, it would be excluded. As a matter of inherent reason, one would suppose this to be an issue to which men with complete devotion to the protection of the right of privacy might give different answers. When we find that in fact most of the English-speaking world does not regard as vital to such protection the exclusion of evidence thus obtained, we must hesitate to treat this remedy as an essential ingredient of the right.

(emphasis mine) Justice Frankfurther then added an Appendix to the Wolf decision listing the "English-speaking" jurisdictions and citations to their courts' rejection of the exclusionary rule. Here is the Appendix:

JURISDICTIONS OF THE UNITED KINGDOM AND THE BRITISH COMMONWEALTH OF NATIONS WHICH HAVE HELD ADMISSIBLE EVIDENCE OBTAINED BY ILLEGAL SEARCH AND SEIZURE.

AUSTRALIA Miller v. Noblet, (1927) S.A.S.R. 385.
CANADA ALTA. Rex v. Nelson, (1922) 2 W.W.R. 381, 69 D.L.R. 180.
MAN. ex v. Durousel, 41 Man. 15, (1933) 2 D.L.R. 446.
ONT. Regina v. Doyle, 12 Ont. 347.
SASK. Rex v. Kostachuk, 24 Sask. 485, 54 Can.C.C. 189.
ENGLAND See Elias v. Pasmore, (1934) 2 K.B. 164.
INDIA ALL. Ali Ahmad Khan v. Emperor, 81 I.C. 615(1).
CAL. Baldeo Bin v. Emperor, 142 I.C. 639.
RANG. Chwa Hum Htive v. Emperor, 143 I.C. 824.
SCOTLAND See Hodgson v. McPherson, (1913) S.C.(J.) 68, 73.

  Twelve years later, the Supreme Court overruled Wolf in Mapp v. Ohio, 367 U.S. 643 (1961), and held that the exclusionary rule was applicable to the states. Strikingly, however, Mapp v. Ohio completely ignored international opinion and international practice. It looked only inwardly, closing its eyes to what Justice Ginsburg has called "the experience and good thinking foreign sources may convey." (Note also that while Frankfurter focused on "English-speaking" nations, he would have reached the same result by looking at all countries; as far as I know, the United States is still the only country in the world with a mandatory suppression remedy for search and seizure violations.)

  Of course, the number of people who want the Supreme Court to rely on foreign law in the interpretation of the Due Process clause and also want a return to Wolf v. Colorado could fit in a phone booth, with room left over for an offensive tackle to enter the phone booth and make a call. But it strikes me as an interesting example.