Congress can pass no laws that are not in pursuance to the Constitution/Bill of Rights -- ESPECIALLY laws based on treaties that infringe on the right of American Citizens to keep and bear arms.
They're shooting blanks. Don't duck!
There have been cases where treaties have been held to supercede the Constitution, and also cases where implementations of treaties have been held to be unconstitutional. So it's murky.
One thing I do know: If I ever see blue hatted UN drones in my neighborhood, I will soon be dead, but I will take a lot of them with me. (What if they are US troops in the blue hats? I just don't think that will ever happen here, so I'm not worried about it.)