A question on the November ballot will ask Illinois voters if insurers should be required to cover birth control as part of their prescription coverage.
Governor Pat Quinn signed the ballot measure over the weekend.
Voters will get to weigh in, but Illinois law won't change whatever the result of the referendum; it's non-binding.
Still, Kim Foxx, the chair of Planned Parenthood of Illinois' board, says it will give legislators a tool to fight any possible attempts to eliminate coverage of contraception.
"We hope the referendum gives the women and men of Illinois the voice to say 'enough. Birth control is basic health care.' "
Foxx says it's important for Illinois to think ahead, in light of the U.S. Supreme Court's recent ruling that allows some private companies to not cover birth control, if it goes against owners' religious beliefs.
Illinois has required prescription plans include birth control coverage for a decade.
Critics say the Democratic-led initiative is an attempt to boost their candidates in what's expected to be a close election.