ORS § 105.070
In an action at law for the recovery of the possession of real property, if either party claims the property as a donee of the United States under the Act of Congress approved September 27, 1850, commonly called the Donation Law, or the Acts amendatory thereto, such party from the date of settlement of the party on the property, as provided in said Acts, is deemed to have a legal estate in fee in the property. The estate shall continue upon the condition that the party performs the conditions required by such Acts, and is unconditional and indefeasible after the performance of such condition. If both plaintiff and defendant claim title to the same real property by virtue of settlement under such Acts, the settlement and the performance of the subsequent conditions shall be conclusively presumed in favor of the party having, or claiming under, the elder patent certificate or patent, unless it appears upon the face of such certificate or patent that it is absolutely void.
ORS 105.070