185.32  Exemptions from chapter.--This chapter shall not apply to any person who is or may become eligible to become a member of any other retirement system provided for by law, or of any retirement system provided for by any ordinance of any incorporated municipality of the state, nor shall this chapter, nor any provisions thereof, be construed as limiting, modifying or enlarging any ordinance of any incorporated municipality of the state; provided, however, that nothing in this chapter shall be construed to bar cities that have adopted the social security plan advanced by the Federal Government.