He is going to the US to stand under US law and this was an FBI initiated and led operation, with the other organisations giving what the FBI terms "substantial and critical assistance", so as far as I can tell this means that outside the US, only the NZ police have assisted in any operational role. "Critical assistance" could even just mean other organisations advising them that it was an appallingly bad idea, depending on how cynically you judge the content of government documentation.

http://www.fbi.gov/news/pressrel/press-releases/justice-depa...