In 1825, the U.S. Supreme Court stated : "The Courts of no country execute the penal laws of another." One hundred and fifty one years later, in a very different world, the United States signed prisoner transfer treaties with its neighbours, Canada and Mexico. Today, through additional bilateral treaties and multilateral treaties negotiated under the auspices of the Council of Europe and the Organization of American States, the United States has prisoner transfer treaty relations with 77 countries. This treatise, designed for prosecutors, defense attorneys and academics, describes in detail the legal basis and operation under these treaties from the perspective of the United States by the former Department of Justice official responsible for their initial implementation