The Bill of Rights tells the US government what it CAN'T do. It has nothing to do with the NRA.
The NRA didn't ban guns from its convention. If you've ever been to a gun show you would probably have been asked to check your guns at the door. You can't carry at many sporting events.
If you don't want to part with your gun, don't go to a private function that requires you to be unarmed. There's nothing unConstitutional about that.