Some one in DC will want certs to make sure all the parts of the firearm were made locally. The steel to make it was virgin, made in the state, no scrap steel, Interstate Commerce, can't prove it was local, coal that made to make the steel was local....
Great idea, don't know if it will fly?
Why accept the burden of proof? They're the ones trying to challenge the law. Let them try to analyze the steel and prove it came from out of state.