The new letter is largely a response to a letter released by the Obama administration last May, which instructed schools to accommodate students based on their stated gender identity. Among other things, this meant schools were required to let transgender students use the bathroom corresponding to their gender identity, and they could not require these students to use special private facilities. The Obama administration also instructed schools not to disclose personal information about transgender students, including their birth name or sex assigned at birth, that “could be harmful to or invade the privacy of transgender students.”

These guidelines were issued under Title IX, the portion of the Education Amendments Act of 1972 that prohibits sex discrimination in education programs that receive federal funding. Especially during the last several years, Obama administration officials took steps to establish “gender identity” as part of “sex” under a number of civil-rights statutes, including Title IX. According to this interpretation, transgender people are protected by law from discrimination in areas from education to health care to employment, in certain cases.

The new letter backs away from this interpretation. The Obama administration’s guidance does not “explain how [its] position is consistent with the express language of Title IX,” the letter states. It also cites the extensive court challenges that have been raised against the Obama-era interpretation. Last spring, 11 states sued the Obama administration over its guidance on Title IX. In August, a federal court issued an injunction preventing the guidelines from being enforced. Scattered lawsuits have additionally been filed across the country challenging school districts’ transgender-friendly bathroom policies, often championed by parents concerned about non-transgender students’ privacy. And court interpretations of other statutes dealing with sex discrimination, including Title VII, have been just as divided.

Now, the Supreme Court is preparing to take up the issue. In March, the Court will hear Gloucester County School Board v. G.G., a case concerning a transgender student in Virginia who sued his school district for access to the boys’ bathroom under Title IX. While a lower court ruled that the student, Gavin Grimm, should be able to use the bathroom according to his gender identity, the Supreme Court stayed the ruling, meaning it is not yet being enforced.

All of this comes back to the Trump administration’s letter. Various court decisions in Gloucester County explicitly referred to the Obama administration’s letter—the Fourth Circuit found that the Education Department’s interpretation of Title IX had “controlling weight” in the case, for example. On Wednesday, the deputy solicitor general notified the Court that the administration’s position had officially changed. With a new interpretation guiding the government, Grimm and other students like him may suddenly find themselves with very different odds of success in court.