(a) A written agreement ratified under this subchapter between a public employer and the bargaining agent supersedes a previous statute concerning wages, salaries, rates of pay, hours of work, and other terms of employment other than pension benefits to the extent of any conflict with the previous statute.
(b) A written agreement ratified under this subchapter preempts all contrary local ordinances, executive orders, legislation, or rules adopted by the state or a political subdivision or agent of the state, such as a personnel board, a civil service commission, or a home-rule municipality.

(c) An agreement under this subchapter may not diminish or qualify any right, benefit, or privilege of an employee under this chapter or other law unless approved by a majority of the votes cast at the secret ballot election held by the bargaining agent to ratify the agreement.