Colorado approves ballot measure designating biological sexes to sports teams

A ballot measure that would require schools and athletic associations to designate biological sexes to sports teams is projected to pass in Colorado, according to Decision Desk HQ.

The initiative, known as Proposition 134, would require schools in addition to athletic associations to designate sports teams based on biological sex – female, male or co-ed/mixed, adding that transgender girls and women can’t compete on girls’ and women’s sports teams.

The ballot measure does note that female athletes can only join sports teams designated for males if “there is no female team offered or available for such sport for such female student or participant.”

The initiative says schools’ governing bodies – which extends to both K-12 schools in addition to colleges and universities – must adopt policies around this requirement and reserves the right for the Colorado commissioner of education to take action against a school district that doesn’t comply with the requirements.

The ballot measure needed a simple majority to pass in the state.

Issues around whether transgender people can use private facilities or play on sports teams that align with their gender identity has been an issue Republicans have heavily leaned into in recent years, which has also divided some Democrats. Republicans have specifically focused on transgender girls and women looking to play on girls’ and women’s sports leagues.

Data from the Williams Institute at the University of California, Los Angeles School of Law estimated in 2025 that there around 300,000 young transgender individuals (ages 13 to 17) in the country in total, with a separate roughly 400,000 transgender people aged 18 to 24 years old in the U.S. in total.