2011 ORS § 166.272¹
Unlawful possession of machine guns, certain short-barreled firearms and firearms silencers

(1) A person commits the crime of unlawful possession of a machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer if the person knowingly possesses any machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer.

(2) Unlawful possession of a machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer is a Class B felony.

(3) A peace officer may not arrest or charge a person for violating subsection (1) of this section if the person has in the persons 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 is an affirmative defense to a charge of violating subsection (1) of this section that the machine gun, short-barreled rifle, short-barreled shotgun or firearms silencer was registered as required under federal law. [1989 c.839 §13a; 1997 c.749 §8; 1997 c.798 §1]