Oregon Revised Statutes Procedure in Criminal Matters Generally § 131.675

When any five or more persons, whether armed or not, are unlawfully or riotously assembled in any county, city, town or village, the sheriff of the county and the deputies of the sheriff, the mayor of the city, town or village, or chief executive officer or officers thereof, and the justice of the peace of the district where the assemblage takes place, or such of them as can forthwith be collected, shall go among the persons assembled, or as near to them as they can with safety, and command them in the name of the State of Oregon to disperse. If, so commanded, they do not immediately disperse, the officer must arrest them or cause them to be arrested; and they may be punished according to law.