Regardless of who or what is responsible, I gather you believe this would be a bad thing. Why?
I don't particularilly welcome the opportunity of other nations to have a hand in writing our laws for us. The world's laws are not going to be brought in line with America's laws; America's laws are more likely to suffer corruption and degredation in the act of being harmonized with the statutes of the rest of the world. This is particularilly distressing to me when I consider the further dammage that would be done to our already shaky second amendment.
I see no need to make any official or binding treaties in this area. A general proclaimitation of the various nation's willingness to co-operate on matters of international law enforcement would surfice. However, I forsee the other option as a greater possibility.