In response to cptsplashdown's original question which basically was, "Is there any law requiring paperwork to be carried with NFA weapons?"
To answer that question and just that question - no, there is no law requiring paperwork (i.e. Form 1, Form4, etc.) to be carried with an NFA weapon.
The discussion quickly became a debate over LEO's outside of ATF asking to see your NFA paperwork.
I agree that only ATF agents can ask specifically for your NFA paperwork. On the other hand, a state and/or local LEO can ask you for proof that your NFA item is properly registered. Your only proof that your NFA item is properly registered is your NFA paperwork. The state and/or local LEO did not ask you specifically for your NFA paper, but simply just for proof of proper registration.
Since we all seem to like analogies in this thread, I give you this analogy:
In some states, LEO's cannot ask for your driver's license unless it is in connection with a traffic violation. For example, in Tennessee only the Tennessee Highway Patrol can check your driver's license when no traffic violation has occured.
So if a LEO says, "Show me your identification," you can identify yourself with a passport, a state issued ID, or your driver's license, etc. because in this scenario you have many choices to satisfy the LEO's request.
In the NFA situation, there is only one way to prove that your NFA item is properly/legaly registered - that is your NFA paperwork.
I think this has been covered, but I'll re-hash it again. You cannot be arrested solely for not having your NFA paperwork with your NFA item. What you can be arrested for is for the state or local violation of possessing a SBR, SBS, MG, etc. These are state/local laws that are not "made up."
The next debate was whether when observing someone with an NFA item if they should automatically be considered to be breaking the law or presumed lawful.
I agree with automatically be considered to be breaking the law. I think all 50 states have a statute stating the effect that SBS, SBR, MG, silencers, etc. are illegal to possess. As for the states that do allow one or more of those items, the statutes are usually written "it is illegal to possess UNLESS properly registered with ATF." So by the way the statute is worded, then someone can be assumed to be breaking the law UNLESS proof is given that they are not. I know that I did not cite actual state laws in this one.
I like the analogy of the marijuana. I would think that in all 50 states, it is illegal to possess/smoke marijuana. If a state allow medicinal use of marijuana, then it still illegal to possess/smoke it UNLESS you have a prescription. So subject possessing/smoking marijuana can automatically be considered to be breaking the law UNLESS the subject can give proof that it is medicinal.
My final opinion - I think cptsplashdown has made up his mind that he is right and there is no changing it.
Yes, this is my first post. I registered just to reply to this thread. Flame away...