Not exactly, if you are in possession of a machine gun and you refuse to show your stamp to a local or state LEO then he would have enough probable cause to make an arrest for a Class C Felony under IC 35-47-5-8, if you were shooting the machine gun at the time then it is a B Felony under 35-47-5-9.
If it is a SBR or AOW and you refuse to show your stamp the LEO would have enough reasonable suspicion to detain you until ATF arrives to sort things out. Larger departments like IMPD have officers detailed full time to ATF. They have both State and Federal arrest powers.
Machineguns and suppressors and sbr's are not illegal . How would the officer have probable cause for an arrest ? Burden of proof lies on them . Detention untill a federal atf or irs agent arrives yes i could see that . I was told by nfa branch that your not required to show the doc's to anyone other than atf or irs agents . If asked I would show local leo's as a measure of faith . In 8 years of shooting i have been asked to show once by a sheriffs deputy when i was shooting a 1919 at my farm in kentucky . He was a nice enough guy we shot the bull for a while he ran a belt through and I never had any problems after that .
Lots of "dumbass" comments being thrown around on this forum. I ask you guys to remember that some of these laws make such little sense that you can't even know what you don't know. For instance, I was going to put a foregrip on a ar pistol. Never occurred to me that this was an offense. Why would it? It's not intuitive? If someone who knew didn't tell me, I could have been a "dumbass."
Let's face it, does the fact that you can own an ar pistol and walk around free, but if you put a stock on it you're a felon make ANY sense at all? You can't know what you don't know, and if you don't know, sometimes you don't even know you should ask.
Let me be on that jury. Hung, hung, hung.