US President Donald Trump's executive order aiming to keep transgender girls and women out of female sports teams comes in the midst of a long-running legal controversy.
Many states have instituted similar bans in recent years, sparking legal challenges, and Trump's action is likely to face lawsuits as well. Here is a look at how the dispute has played out in court so far, and how it could continue.
There is no federal statute on the issue, but more than 20 Republican-led states have passed laws banning transgender girls from participating in school sports. Proponents of these laws say they are needed to ensure fairness in girls' sports by keeping out transgender athletes who may have a biological advantage. Opponents say they are discriminatory and transgender girls do not necessarily have an advantage.
Trump's order seeks to do the same thing as state laws - prevent transgender girls and women from competing on female teams.
It relies partly on the authority of the U.S. Justice Department to bring enforcement actions under Title IX, the federal law that bars sex discrimination in education and requires schools to offer girls an equal opportunity to play sports. Under Trump's interpretation of Title IX, the law forbids transgender girls from playing in girls' sports.
It also instructs the federal government to begin enforcement immediately by cutting off federal funding for schools that do not comply.
Transgender athletes and their families have sued to block state bans alleging that the laws violate their right to equal protection under the U.S. Constitution, as well as Title IX, which they interpret to protect transgender girls' right to play in girls' sports.
They have cited a 2020 U.S. Supreme Court ruling finding that discriminating against transgender people is discrimination on the basis of sex, which is prohibited by Title VII, a federal law banning employment discrimination. Though they are separate laws, Title IX and Title VII have often been interpreted similarly by courts.
Several legal challenges have succeeded in blocking enforcement of state laws, at least against the plaintiffs who brought those challenges.
The 9th U.S. Circuit Court of Appeals, which hears appeals from nine western states, struck down Idaho's law against transgender athletes playing in the sex category matching their gender identity, finding that it likely discriminated on the basis of sex. Idaho was the first state to pass such a law.
The 9th Circuit and the 4th Circuit, which covers several mid-Atlantic and southeastern states, have also blocked bans from being enforced against specific plaintiffs in West Virginia and Arizona. A federal judge in Concord, New Hampshire has blocked that state from enforcing its ban against two plaintiffs.
However, a state court judge last month allowed Nassau County, New York to enforce a law prohibiting transgender girls and women from playing in female sports at county-owned athletic facilities.
The rulings so far have come at early stages in the litigation, blocking enforcement while the lawsuits remain pending. Any of the cases could eventually be appealed to the Supreme Court, which is likely to ultimately decide the issue. The Supreme Court declined to hear an appeal of the 4th Circuit ruling at a preliminary stage.
Former Democratic President Joe Biden's administration proposed a federal rule preventing educational institutions that receive federal funding from categorically excluding athletes based on their transgender status. The proposed rule, based on Title IX, would have allowed limitations on participation for reasons of fairness or to prevent injury.
The Biden administration dropped the rule in December, citing unfavorable public comments and ongoing litigation over how Title IX applies to the issue.
