To date, nine instruments have been signed, allowing prisoner transfer between the United States and 22 countries. In addition to serving rehabilitative and humanitarian goals, the treaties improve relations between the involved governments. Before transfer is allowed under the treaties' terms, prisoners must agree not to challenge their convictions upon entering the United States. This requirement presumptively raises the issue of whether transferred prisoners validly waive their constitutional right to habeas corpus. A related issue is whether the treaties place an unconstitutional condition upon the prisoners' right to habeas corpus. A test for what constitutes a valid waiver of habeas corpus has never been firmly set by the U.S. Supreme Court, chiefly because of the enigmatic nature of the voluntariness standard. Thus, analyzing the treaties through the waiver standard yields an inconclusive determination that the treaties are probably constitutional. Focusing on the treaties through the unconstitutional-conditions doctrine leads to the conclusion that the prisoner's waiver of judicial review is valid. 207 footnotes.