During President Barack Obama’s last year in office, his attorney general, Loretta Lynch, made a promise to transgender Americans — and particularly trans students in public schools: “The Department of Justice and, indeed, the entire Obama administration want you to know that we see you, we stand with you, and we will do everything we can to protect you going forward. And please know that history is on your side.”

This vow appears to be coming to an end under President Donald Trump. Quietly last week, the Trump administration began undoing the promise’s basis — by pulling away its legal defense of trans students’ rights in a potentially pivotal court battle.

The decision is actually no surprise. A few months before Trump was elected president, the Obama administration sent out guidance to federally funded public schools arguing that trans students’ rights are protected under existing federal civil rights law, so schools need to let these students use the bathrooms and locker rooms that align with their gender identity. Trump said the guidance, even though it was not legally binding, was an example of federal overreach, and he vowed to undo it once he was elected.

Before Trump took office, though, several states sued over the guidance, arguing that the Obama administration was misinterpreting federal civil rights law. Until last week, the Justice Department stood against those states. It made the case that Title IX, a federal law, because it bans sex discrimination also bans anti-trans discrimination, since discrimination against trans people is rooted in stereotypes and prejudices of what people should be like based on the sex they were assigned at birth.

The Trump administration appeared to abandon the case in court with a short filing on Friday — just one day after Attorney General Jeff Sessions was sworn in. In the joint filing (with the states suing the federal government), the Justice Department dropped its formal request for a federal appeals court to stay a lower court’s nationwide injunction on the Obama administration’s pro-trans guidance. The department also asked the courts to cancel oral arguments for the case, as both sides “are currently considering how best to proceed in this appeal.”

In other words, the Trump administration is effectively letting the court’s injunction on the Obama administration’s pro-trans guidance stay in place — and it looks like the new administration is prepared to stop defending the guidance in court altogether. (The Trump administration didn’t respond to questions about this move.)

The decision is big not just for this particular case but for trans rights in general. The Obama administration took a widely welcoming interpretation of federal civil rights law to include trans people. The Trump administration, with its latest legal moves, is apparently not going to take a similar approach — and that could be very bad news for trans Americans.

The Obama administration’s guidance was trying to clarify a key dispute in civil rights law

Under most states’ laws and federal law, trans people are not explicitly protected from discrimination in the workplace, housing, public accommodations, and schools. This means that a trans person can be fired, evicted, kicked out of a business, or denied the correct bathroom facility just because an employer, landlord, business owner, or school principal doesn’t abide by or acknowledge the trans person’s gender identity.

The Obama administration, under the urging of LGBTQ groups and a federal agency that works on workplace discrimination, adopted a different view of the law. It argued that federal civil rights laws do protect trans people in the workplace, housing, and schools.

The argument: Federal civil rights law already prohibits sex discrimination. And the ban on sex discrimination also applies to gender identity, since discrimination based on gender identity — and against trans people — is fundamentally rooted in expectations of what people of certain sexes assigned at birth should be like.

Under this view, school officials are discriminating — and violating civil rights law — if trans students are blocked from using a bathroom or locker room for their gender identity. After all, forcing trans people to use the facility that doesn’t align with their gender identity acts as a reminder that society still isn’t completely willing to accept them and their identities, even if trans people pose no danger to anyone else.

So the Obama administration sent out guidance to public schools making this more formal policy, leading to the legal battle that the Trump administration is now letting up.

But until courts validate the guidance, it’s really a legally non-binding set of guidelines. That’s why this court battle mattered: It could have given more weight to the Obama administration’s position on federal civil rights law.

The outcome of the legal battle could be a big deal. If courts approve of the Obama administration’s interpretation of federal civil rights law, it could effectively expand existing civil rights protections that explicitly ban discrimination based on race and sex, among other traits, to explicitly include gender identity. And that could, in turn, bleed over to federal civil rights laws beyond Title IX and education — such as the Civil Rights Act’s protections in the workplace and the Fair Housing Act’s provisions for housing. (A case dealing with these issues, particularly school bathrooms, is actually in front of the Supreme Court right now.)

It might seem strange that the battle for civil rights law has so much to do with bathrooms and locker rooms. All of this goes back to a political firestorm that broke out in 2016 when North Carolina passed HB2, which prohibits trans people in the state from using the bathrooms and locker rooms that align with their gender identity in schools and government buildings. But it is also part of a broader political strategy to limit the spread of LGBTQ rights in America, built largely on a myth.

This entire issue is based on a myth about trans people and bathrooms

Underlying this entire issue is a big myth about trans people, nondiscrimination laws, and bathrooms.

According to supporters of North Carolina’s HB2 and other opponents of the Obama administration’s guidance, letting trans people use the bathroom for their gender identity would pose a public safety risk. They claim that if trans people can use the bathroom that aligns with their gender identity, men will take advantage of such policies to disguise themselves as trans women and sneak into women’s bathrooms or locker rooms to sexually assault or harass women.

Some religious conservatives have latched onto this myth to oppose laws that ban discrimination against sexual orientation and gender identity in the workplace, housing, public accommodations, and education — particularly after a big win in Houston, where voters struck down a local nondiscrimination law after opponents of the ordinance trumpeted the bathroom myth. North Carolina's law, for instance, came after Charlotte added sexual orientation and gender identity to its nondiscrimination protections for public accommodations. (More on all of that history in Vox's broader explainer.)

Indeed, this is the argument that Texas, the biggest state in the lawsuit against the Obama administration’s guidance, has repeatedly cited to defend its position.

But even if trans people are allowed to use the bathroom for their gender identity, sexual assault remains illegal. So a legal deterrent to deviant behavior already exists.

There's also no evidence that nondiscrimination laws — and other policies that also let trans people use the bathroom for their gender identity — lead to sexual assault in bathrooms and locker rooms. In two investigations, Media Matters confirmed with experts and officials in 12 states and 17 school districts with protections for trans people that they had no increases in sex crimes after they enacted their policies.

Conservatives usually counter that there are examples of men sneaking into women's bathrooms to attack women. But as PolitiFact reported, none of the examples cited in the US happened after a city or state passed a nondiscrimination law or otherwise let trans people use the bathroom or locker room for their gender identity. Instead, these seem to be examples of men doing awful things regardless of the law — which has, unfortunately, happened since the beginning of civilization.

One example is a case in Toronto, Canada, which now has a nondiscrimination law, in which a man disguised himself as a woman and attacked women in shelters. But the attacks happened months before Ontario (Toronto's province) protected trans people in a nondiscrimination law. So the law couldn't have been the cause.

Still, the myth has persisted — trickling up in some way or another all the way to legal battles over federal laws. And it’s a big reason the Trump administration is now poised to stop defending trans students’ civil rights in court.

Watch: The big myth behind anti-transgender bathroom bills