C.R.S. § 24-51-308

Any municipality affiliated with the association may authorize the city manager and key management staff who report directly to the city council or city manager to make a one-time, irrevocable election to be exempted from membership. If so authorized, the city manager and key management staff shall make a written election to become a member or to be exempted from membership within sixty days after becoming employed in the position. In the absence of a written election, such person shall be a member.