A member retired for service under this part whose last employment was in the California State University, as a member of the Defined Benefit Program or the Public Employees’ Retirement System, may serve as a member of the teaching staff of the California State University and shall be subject to the employment limitations as provided by the Public Employees’ Retirement Law (Part 3 (commencing with Section 20000) of Division 5 of Title 2 of the Government Code).