The United States Supreme Court ruled on Tuesday that individual states may prohibit transgender women and girls from competing on female sports teams in public schools and universities. The 6-3 decision, authored by Justice Brett Kavanaugh, upheld laws in Idaho and West Virginia and effectively validates similar statutes in 25 other Republican-led states. The court found that such restrictions do not violate Title IX, the federal civil rights law barring sex discrimination in education, nor the Equal Protection Clause of the 14th Amendment. The immediate consequence is that states may now enforce eligibility rules based on biological sex without facing federal constitutional or statutory challenges, a legal shift that directly affects an estimated 122,000 transgender teenagers who participate in high school sports, according to the Williams Institute at UCLA.

The court’s conservative majority grounded its reasoning in what it described as the inherent physical differences between the sexes, arguing that separate teams are permissible and that states have a substantial interest in ensuring competitive fairness and safety. Kavanaugh wrote that “the Constitution and Title IX do not require an overhaul of women’s and girls’ sports throughout America.” The three liberal justices concurred in part, agreeing that the laws do not breach Title IX, but dissented on the constitutional question, with Justice Sonia Sotomayor contending that the majority had acted on “assumptions rather than facts” and should have allowed lower courts to develop a fuller evidentiary record. The Trump administration, which had backed the states in litigation, celebrated the outcome as a “big win,” while the American Civil Liberties Union, representing the transgender plaintiffs, called the ruling “heartbreaking” and vowed to continue legal challenges.

The decision does not impose a nationwide ban; transgender students may still compete in states without such laws, including California and New York, which explicitly protect their participation. However, the ruling is the latest in a sequence of Supreme Court judgments that have curtailed transgender rights. Last year, the court upheld Tennessee’s ban on gender-affirming medical care for minors, and earlier this year it sided with parents who objected to California school policies designed to protect transgender students. Viewed from Washington, the sports cases consolidate a legal framework in which classifications based on biological sex are treated as distinct from discrimination on the basis of gender identity, a distinction that is likely to shape future litigation over bathroom access, identity documents, and military service.

The two cases before the court involved Becky Pepper-Jackson, a West Virginia high school student who had been taking puberty blockers and competing in girls’ track and field, and Lindsay Hecox, an Idaho college student who sought to try out for women’s cross-country. Both had won injunctions in lower federal courts, which found the bans likely discriminatory. The Supreme Court’s reversal removes those injunctions and signals that similar challenges in other circuits will face a hostile bench. The ruling explicitly leaves open the question of whether schools may voluntarily permit transgender athletes to compete, a matter currently being litigated in lower courts. Meanwhile, the International Olympic Committee and the NCAA had already moved to restrict transgender women’s participation in elite female sport, a trend that this judicial endorsement is expected to reinforce.