The Trump administration on Friday took one of its most aggressive steps yet to legalize anti-transgender discrimination by telling the Supreme Court that federal law allows firing workers solely for being transgender, arguing a Michigan funeral home could fire a transgender woman because she wanted to wear women’s clothing on the job.

Although the administration was expected to take the stance — and had previously said firing workers on the basis of gender identity is legal under federal law — the latest court filing asks the nation’s top court to establish federal case law in a potentially sweeping setback for LGBTQ rights nationwide.

The case is a dispute over the word “sex.” Title VII of the Civil Rights Act of 1964 bans workplace discrimination because of sex, but the court’s justices have never decided what, precisely, the term means for LGBTQ workers.

The Justice Department’s brief on Friday contends the word refers to a person’s “biological sex” and, further, that transgender discrimination isn’t addressed by a 1989 Supreme Court ruling that found Title VII bans sex stereotyping.

“Title VII does not prohibit discrimination against transgender persons based on their transgender status,” says a filing by the Justice Department, adding, “It simply does not speak to discrimination because of an individual’s gender identity or a disconnect between an individual’s gender identity and the individual’s sex.”

Rather, the administration contends, “Title VII prohibits treating an individual less favorably than similarly situated individuals of the opposite sex.”

The administration said transgender workers could still be protected by Title VII, but not discrimination based on the fact that they are transgender.

A Supreme Court ruling in favor of the administration’s position could set off cascading ramifications for LGBTQ Americans by asserting that laws banning sex-based discrimination must be construed narrowly, and it would have no application for sexual orientation or gender identity — a decision that would likely overflow far beyond workplaces.

No federal law explicitly bans anti-LGBTQ discrimination, but the term “sex” appears in countless state and federal laws, and various policies, that ban discrimination. They have often been used by courts and agencies to protect LGBTQ people in a range of settings — from jobs and schools to doctor’s offices — and a Supreme Court ruling that finds sex absolutely does not protect LGBTQ people could unravel previous court rulings and narrow the meaning of policies.

The administration’s argument against LGBTQ rights matches the advocacy of conservative Christian groups, which claim Congress only intended to ban discrimination because someone is male or female — saying the sexes cannot be treated differently. Their argument says interpreting the term “sex” more broadly effectively rewrites the law, and only Congress, not courts, has that license.

The counterargument from LGBTQ advocates and several lower courts, however, is that the intent of lawmakers does not limit a law’s reach, but rather its meaning is defined by the statute’s plain text. They say anti-transgender discrimination can result from a person defying traditional sex stereotypes or because the person transitioned from one sex to another — and thus, it is inherently a type of sex discrimination.

The case at issue is one of three currently before the court about the rights of LGBTQ workers under Title VII — and the only one concerning a transgender worker.

Aimee Stephens had presented as a man when she started her job in 2007 at R.G. & G.R. Harris Funeral Homes in Michigan. Six years later, after Stephens announced plans to transition to a woman, the owner, Thomas Rost, fired her.

In siding with Stephens last year, a 49-page opinion led by Judge Karen Nelson Moore at the Court of Appeals for the 6th Circuit found that “The unrefuted facts show that the Funeral Home fired Stephens because she refused to abide by her employer’s stereotypical conception of her sex.”

“Discrimination against employees, either because of their failure to conform to sex stereotypes or their transgender and transitioning status, is illegal under Title VII,” the court went on, explaining “it is analytically impossible to fire an employee based on that employee’s status as a transgender person without being motivated, at least in part, by the employee’s sex.”

But the Justice Department counters that when the Civil Rights Act passed in 1964, “the ordinary public meaning of ‘sex’ was biological sex. It did not encompass transgender status, which Stephens and the Sixth Circuit describe as a disconnect between an individual’s biological sex and gender identity. In the particular context of Title VII — legislation originally designed to eliminate employment discrimination against racial and other minorities — it was especially clear that the prohibition on discrimination because of ‘sex’ referred to unequal treatment of men and women in the workplace.”

The case for Stephens was brought by the Equal Employment Opportunity Commission, a largely autonomous federal agency that championed her cause and argues Title VII covers LGBTQ people, including on the basis of sexual orientation. But now that this case is before the Supreme Court, per typical procedure, the solicitor general at the Justice Department has taken over to represent the government.

In Stephens’ case, this means government lawyers now say it was legal to fire her — thereby holding the opposite position as the EEOC even though it is representing the EEOC. As such, it says the 6th Circuit ruling should also be reversed.

Under former president Barack Obama, the Justice Department asserted that Title VII did, in fact, protect transgender workers and vowed to argue accordingly in court. But the year president Donald Trump took office, his former attorney general, Jeff Sessions, reversed that stance.

Represented by the Christian conservative group Alliance Defending Freedom, the funeral home filed a separate brief, filed Friday, that portrays the case as a fight over the essence of gender norms in society, playing off fears stoked by conservatives about transgender people preying on women in bathrooms.

“Redefining sex discrimination will cause problems in employment law, reduce bodily-privacy protections for everyone, and erode equal opportunities for women and girls, among many other consequences. Congress, not the courts, is the institution best positioned to balance those considerations,” the group said.

The group further argued only Congress can define the term: “In 1964, as today, sex discrimination meant differential treatment based on a person’s biological sex, something fixed and objectively ascertained based on chromosomes and reproductive anatomy. It occurs when employers favor men over women, or vice versa.”

But the Supreme Court hasn’t held quite such a narrow view in the past. In the case of Price Waterhouse v. Hopkins — the 1989 sex stereotyping case in which a female employee claimed she wasn’t promoted because she didn’t present femininely enough — the court found that Title VII’s ban on sex discrimination also bans sex stereotyping in the workplace.

Yet the Justice Department said that case doesn’t apply here. “Harris Homes did not discriminate against Stephens based on sex stereotypes in violation of Title VII,” government lawyers wrote. “It terminated Stephens for refusing to comply with Harris Homes’ sex-specific dress code. Since the court of appeals did not address and Stephens does not challenge that dress code in this Court, it must be assumed that the dress code burdens men and women equally.”

The high court also found in Oncale v. Sundowner Offshore Services in 1998 that Title VII’s ban on sex discrimination also prohibited workplace harassment in the case of a man who was perceived to be gay.

The Supreme Court will hear oral arguments in the three Title VII cases Oct. 8, including two that ask if Title VII covers sexual orientation. The Trump administration is expected to submit its argument to the Supreme Court in those latter cases by Aug. 23.