Okla. Stat. tit. 21, § 21-1317: Presence after unlawful purpose becomes known

Where three or more persons assemble for a lawful purpose and

afterwards proceed to commit an act that would amount to riot if it

had been the original purpose of the meeting, every person who does

not retire when the change of purpose is made known, except public

officers and persons assisting them in attempting to disperse the

same, is guilty of a misdemeanor.