(1) it's a violation if the suspect knowingly possesses any machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer.

(3) a peace officer may not arrest or charge a person for violating subsection (1) of this section if the person has in their immediate possession documentation showing that the machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer is registered as required under federal law

(4) it's an affirmative defense to a charge of violating (1) that the machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer was registered as required under federal law