(a) Except as provided in paragraph (b) and section 3A.17, this chapter applies to members of the legislature in service after July 1, 1965, who otherwise meet the requirements of this chapter.

(b) Members of the legislature who were elected for the first time after June 30, 1997, or members of the legislature who were elected before July 1, 1997, and who, after July 1, 1998, elect not to be members of the plan established by this chapter are covered by the unclassified employees retirement program governed by chapter 352D.

(c) The post-July 1, 1998, coverage election under paragraph (b) is irrevocable and must be made on a form prescribed by the director. The second chance referendum election under Laws 2002, chapter 392, article 15, also is irrevocable.