Oregon Revised Statutes Agriculture § 565.240

The board may make and enforce all rules and regulations necessary for the proper conduct and management of their respective fairs. It may appoint such marshals or police as may be necessary to keep order and preserve the peace during the time and at the place of holding the fairs and at all other times when the board deems such appointments necessary for the preservation of the peace and the protection of public and private property upon the fairgrounds. The officers so appointed have the same authority for the preservation of order and making arrests upon the grounds as would a deputy sheriff.