ORS 305.260

No former officer, clerk or employee of the Department of Revenue shall represent any taxpayer in any claim or controversy pending in the Department of Revenue or in the magistrate division of the tax court during the employment of the former officer, clerk or employee therein, nor shall the former officer, clerk or employee in any manner or by any means, aid in the prosecution of any such claim, within two years next after the former officer, clerk or employee has ceased to be such officer, clerk or employee.