US states can prohibit biologically male athletes who identify as women or girls from competing against female athletes, the US Supreme Court ruled in a 6–3 decision on Tuesday.

In the majority opinion, Justice Brett Kavanaugh wrote that individual states did not violate federal US civil rights legislation prohibiting sex-discrimination, or the Equal Protection Clause of the Constitution, by determining athletic eligibility based on biological sex, rather than “gender identity.”

He likewise ruled that schools need not make an exception for biological males who have taken puberty blockers or cross-sex hormones.

Even the three dissenting judges agreed in part with the ruling.

The result upholds the constitutionality of such restrictions in at least 27 of the fifty US States.

The International Olympic Committee in March announced a new policy under which men who believe themselves to be women will be forbidden from competing in the women’s category.