Was either NFA 1934 or GCA 68 ever voted on by congress and signed into law by a president? If not, they're both unconstitutional. Getting a veto-proof majority of strict-constitutionalist legislators and passing reasonable laws should be a top priority, but the swamp will never allow that to happen!
Voted on by Congress, and signed into "law" by the President - does NOT make laws Constitutional!
That decision rests on SCOTUS, and they don't always get it right. Liberals want to legislate, and modify the Constitution from the bench.