A divided Supreme Court on Tuesday upheld two state laws barring the participation of transgender female athletes from girls’ and women’s sports teams.
The court’s 6-to-3 ruling deals with laws from West Virginia and Idaho but has implications for the 25 other states with similar restrictions, and for athletes who compete in school and collegiate sports nationwide.
The Trump administration, which backed the state bans, has targeted the participation of transgender athletes in sports amid a national rollback of rights for transgender people. President Trump directed federal agencies last year to withdraw funding from schools that allow transgender athletes in girls’ and women’s sports.
The cases attracted intense public interest, with Olympians and other elite athletes watching closely and submitting legal briefs in support of each side. In March, the International Olympic Committee barred transgender athletes from competing in the women’s category of the Olympics and said that all participants in those events must undergo genetic testing. The N.C.A.A. announced last year that it would bar trans women from competing in women’s sports.
At the Supreme Court, Becky Pepper-Jackson, a high school student from West Virginia, and Lindsay Hecox, a college student in Idaho, challenged their respective state’s laws, which both required that participation on sports teams for girls be based on “biological sex,” defined as a person’s birth sex.
Tuesday’s ruling divided the court along ideological lines, with the conservative majority allowing states to determine eligibility for women’s and girls’ sports based on biological sex.
The Constitution and Title IX “do not require an overhaul of women’s and girls’ sports throughout America,” wrote Justice Brett M. Kavanaugh.
“Allowing a biological male athlete to compete on a girls’ team necessarily displaces or disadvantages a female athlete — replacing her on the roster, knocking her out of the starting lineup, reducing her playing time, depriving her of a medal and the like,” he wrote. “That hard reality of sports cannot be ignored or swept under the rug.”
Justice Kavanaugh, an avid sports fan and longtime girls’ basketball coach, concluded the majority opinion by emphasizing that the desire of transgender female athletes to compete “warrants respect.”
“No student-athlete on either side of the issue, whether a biological female or transgender, deserves to be ostracized or vilified,” he wrote.
The court’s three liberal justices agreed with the majority’s decision to reject the claims under Title IX, the federal law which has led to major increases in opportunities and participation for women in sports. But they said their colleagues had prematurely ended the constitutional challenge and should have allowed lower courts to determine whether Ms. Pepper-Jackson, a transgender girl who has not gone through male puberty because of medication, has an athletic advantage over other girls.
“These circumstances demand exercising judicial restraint, not rushing to answer conclusively difficult questions without sufficient evidentiary development,” wrote Justice Sonia Sotomayor, who read a summary of her dissent from the bench in a sign of her deep disagreement with the majority.
The court, she added, denies transgender athletes the benefits of participating in school sports “simply because it thinks they have an inherent athletic advantage, even if the facts show that they do not,” she wrote. “Sports, of course, are often zero sum, but the law need not and should not be.”
Lower courts had blocked enforcement of the laws, allowing Ms. Pepper-Jackson, 16, to compete on her high school track team while the litigation was underway. She is the only known athlete in West Virginia who would be subject to the law, and the court’s decision means she will no longer be allowed to participate on the girls’ team.
In both cases, the athletes asserted that the state laws violate the Constitution’s guarantee of equal protection, which requires the government to have valid reasons for treating people differently. Ms. Pepper-Jackson, who initially sued to join her middle school’s girls’ cross-country team when she was 11, also claimed that West Virginia’s statute violates the federal Title IX statute by denying her access to the school’s athletic program and treating her worse than her peers.
In a statement, one of the lawyers for the athletes called the court’s decision a “heartbreaking ruling for our clients and transgender girls like them who’ve asked for nothing more than the same opportunities afforded to their peers.” said Joshua Block, senior counsel for the American Civil Liberties Union’s L.G.B.T.Q. and H.I.V. Project.
Lawyers for the states and the Trump administration had countered that the participation of transgender female athletes threatens to undermine five decades of progress since the passage of Title IX. A small percentage of Americans, about 1.3 percent, identify as trans and an even smaller number participate in competitive sports.
Gov. Patrick Morrisey of West Virginia called the decision “one of the most important victories for women’s athletics since the enactment of Title IX itself.” He added: “This began in West Virginia, but its impact reaches every corner of the country. Future generations of female athletes will benefit from the certainty, fairness and opportunity this decision protects.”
Mr. Trump also cheered the Supreme Court’s ruling on social media, writing, “Wow! That takes that ridiculous situation off the table!!!”
Efforts to bar transgender athletes from women’s sports have seen broad support in polls. A New York Times/Ipsos poll conducted last year found that nearly 80 percent of Americans, including two-thirds of Democrats, opposed allowing transgender women to compete in women’s sports.
The Supreme Court had not previously addressed the legal issues surrounding transgender athletes, but has moved against transgender rights in other areas in recent years. After protecting transgender people from workplace discrimination in a 2020 decision written by Justice Neil M. Gorsuch, a Trump appointee, the court in June upheld a Tennessee law that prohibits certain medical treatments for transgender adolescents. Last May, the conservative majority also allowed the president to start enforcing a ban on transgender troops in the military.
Tuesday’s decision does not address the legality of rules in other states such as California, where transgender girls have had the right to compete in girls’ events since 2013. The court called that a “debated policy question.”
The 27 states that have enacted bans on trans athletes over the past several years all had Republican-led legislatures. But ballot questions addressing transgender athlete participation are moving forward in Colorado and Washington, both Democrat-led states.
Kristen Waggoner, the president of the Alliance Defending Freedom, which defended the bans in Idaho and West Virginia, said states that do not currently prohibit transgender athletes from playing girls’ sports should expect to be targeted by conservative advocates seeking the passage of such laws.
During oral arguments in January, the justices grappled with concerns about fairness, scientific uncertainty and discrimination and questions about when boys and girls can legally be treated differently.
Two appeals courts had sided with the student athletes and prevented the laws from being enforced.
In Idaho, a federal judge said that promoting equal athletic opportunities for men and women was an important government interest, but that categorically barring Ms. Hecox did not advance those goals because of the medical treatment she receives. She is treated with testosterone suppression and estrogen that she argued reduced any competitive advantage she might otherwise hold.
Ms. Hecox had tried to drop her case before it reached the Supreme Court because she has stopped playing women’s sports. The justices had deferred a decision about what to do with her case until after argument, and the majority said Monday that her case was not moot.
In West Virginia, a district court judge, Joseph R. Goodwin, upheld the state law. He found that it did not violate the Constitution or Title IX, and concluded that “it is generally accepted that, on average, males outperform females athletically because of inherent physical differences between the sexes.”
But a divided panel of the U.S. Court of Appeals for the Fourth Circuit said the law could not be enforced against Ms. Pepper-Jackson.
Juliet Macur, Amy Harmon and Erica L. Green contributed reporting.