I am not sure on what basis a law enforcement official could simply demand to see a tax stamp, assuming that the item can be legally owned (with appropriate paperwork) in that area. They can come up and ask, but a LEO cannot simply stop me from engaging in a legal activity, demand documents, and take some kind of action if I don't provide them. I know the political elites have done their best to destroy it but the 4th amendment still carries at least a little water most places.
For a government agent to seize me and make me produce paperwork it would seem that the agent would need at least reasonable articulable suspicion that a crime is being committed or about to be committed. If one can with proper paperwork own a supressor, then having a supressor is not sufficient RAS of a crime. Rather it is a mere hunch or sheer speculation that the person may not have a stamp. Thus going an detaining the person would seem to be a pretty big 4th amendment violation.
I am aware of a case that addressed a similar issue in MA. It was about carrying a gun. There is was legal to carry with a permit and illegal to carry without one. An officer saw indicia of a person carrying a gun, stopped them and demanded a permit be shown. The courts in essence said there was no RAS, because a having a gun is not indicia of illegal activity since one can be carried legally under some circumstances.
An analogy would be driving a car. I can drive if I have a license. However, if I do not have a license it is illegal. A cop cannot just pull over any driver to check and see whether or not that driver has a license. Rather the cop would need reasonable, articulable facts that lead him to suspect the person does not have a license.
Now a government agent could walk up and ask you to voluntarily show your stamp. They very likely will not phrase it that clearly, and although not technically a demand it will sound much more like one than a request to the average Joe. You can waive your rights, and that's on you.
Never been asked...nor would I produce such paperwork for ANYONE other than law enforcement personnel whose job it is to inquire about such things.
Assuming it is a private range, the owners or workers can make whatever rules (within some constraints) that they want. If you don't like it go somewhere else. They can do a lot of things that would be wholly improper for any LEO to do. For example one range I have gone to wants you to put your name, provide photo ID, fill out a form, and leave your DL#. If a cop walked up to me out of the blue and asked for all that it would be a very different situation.