Maybe they’re shooting a friend’s gun. Is that legal?
First I'm not a lawyer, but no, to shoot a deer in Wisconsin you have to have a deer tag, which a felon can't purchase. The firearm isn't the issue. Whether a felon can posess a firearm in Wisconsin, I don't know, my guess is he can't.
In Illinois, forget felon, if you don't have an FOID, are a registered firearm owner, pick a firearm up, you've committed a crime in most circumstances, perhaps a felony if a handgun.
If they can shoot it without possessing it, I suppose, it would be. But even renting a gun for use only in the particular indoor range renting it to them is interpreted as "possessing" it by our FRiends at the BATFE.