When directed by the Governor, as prescribed in ORS 30.570, it shall be the duty of the district attorney to commence the action therein provided for accordingly. In all other actions provided for in ORS 30.510 to 30.640 it shall be the duty of the proper district attorney to commence such action, upon leave given where leave is required, in every case of public interest, whenever the district attorney has reason to believe that a cause of action exists and can be proven, and also for like reasons in every case of private interest only in which satisfactory security is given to the state to indemnify it against the costs and expenses that may be incurred thereby.
Oregon Legal Code