Why the US will (or should) never agree to a World Court
This essay says it best.
The fundamental issue is that Americans believe that the govt takes its authority from the people, as much as they are willing to grant. And that we have the right to rescind such authority and replace that government. We cannot and should not grant powers to a world govt that we do not grant by basic tenet to our own soverign govt. Another minor detail is that many of the proposals subvert the US Constitution.