Oregon Revised Statutes Highways, Roads, Bridges and Ferries § 377.737

(1) To determine whether a person is giving or receiving, or has given or received, compensation or anything of value as defined by the Department of Transportation by rule for displaying a sign, the department may issue an investigative demand upon any person it reasonably believes may have relevant documents or information.

(2) If any person after being served an investigative demand under subsection (1) of this section fails or refuses to obey the demand, the Department of Transportation may request that the Department of Justice apply to an appropriate circuit court and, after a hearing, request an order requiring compliance with the demand.