Oregon Revised Statutes Agriculture § 565.640

The peace officers of a county fair board or of a society mentioned in ORS 565.610, during the continuance of each annual fair or other public event or meeting, and for three days prior and two days subsequent thereto, on the grounds owned or occupied by the county fair board or society for fairs, exhibitions or other public events or meetings, shall have all the authority of a deputy sheriff and may make arrests for violations of the provisions of ORS 565.610 to 565.650 or other laws of this state, or the rules or regulations of the fair board or society.