The US Supreme Court has made a landmark ruling, allowing states to ban transgender biological males from competing in girls' sports.
The court's 6-3 opinion states that West Virginia and Idaho's laws banning biological males from girls' sports do not violate the Constitution's equal protection clause or Title IX.
Two biological male athletes, represented by the ACLU and Cooley Legal, had sued the states to allow them to compete with girls.
Justice Brett Kavanaugh wrote in the majority opinion that Title IX was enacted in 1972 to promote equal opportunity for female student-athletes, but that schools can still maintain separate sports teams for women and girls based on biological sex.
"To provide equal opportunity for female athletes, schools do not merely maintain one soccer team, one basketball team, one ice hockey team, and one lacrosse team that are equally open to female and male athletes," Kavanaugh wrote.
Justice Clarence Thomas delivered a concurring opinion, slamming the mental illness of "gender dysphoria" and stating that it does not resemble the immutable characteristics on which the court's precedents have applied heightened scrutiny.
Thomas wrote that men and boys with gender dysphoria are not women or girls, even if they believe they are.
He argued that sex is an immutable "biological" characteristic, and that the terms "man," "woman," "boy," and "girl" correspond to adults and children of each sex.
Justice Kentanji Brown Jackson and Justice Sonya Sotomayor wrote dissenting opinions, arguing that the court was wrong to hold that Title IX protects against discrimination solely on the basis of "biological sex."
The ruling is expected to impact up to 27 states with similar laws on the books.
The Supreme Court's decision is a major victory for states that have enacted laws restricting transgender athletes' participation in school sports.
The cases, known as West Virginia v. B.P.J. and Little v. Hecox, have been closely watched throughout the term.
The court's ruling is expected to have far-reaching implications for transgender athletes and their families.
President Trump had signed an executive order last year that prohibits educational programs that receive federal dollars from allowing transgender girls and women to play on the teams that align with their gender identity.
