Something big just quietly happened to the Affordable Care Act. More than a half decade after the law’s passage, the U.S. Department of Health and Human Services has explicitly ruled that hospitals, clinics, and other health-care providers can’t discriminate against patients on the basis of gender identity. This covers a lot of scenarios: denying a transgender person insurance coverage for hormonal therapy just because they’re trans; refusing to provide sex-specific treatment, such as a hysterectomy, because a patient doesn’t look like a woman; harassing patients for the way they express their gender, which might include everything from clothing and hairstyle to voice and mannerisms; and more.

This ruling will have concrete consequences for a lot of people. A lot of discrimination against LGBT people happens in health care, and this can have significant consequences.

But it’s also legally significant because of the way the agency interpreted the law. HHS said “gender identity” is part of “sex discrimination,” which is also outlawed under Title VII, a 1964 law which has to do with employers, and Title IX, a 1972 law having to do with education. This is the latest in a series of administrative interpretations that are helping to establish legal protections for people with a wide range of gender identities. That will likely help transgender people more successfully pursue discrimination cases in all spheres of life—including health care.

The first move toward this ruling happened at the law’s inception. “Since 2010, we have had a prohibition on discrimination on the basis of sex in health care,” said Elizabeth Sepper, a law professor at Washington University in St. Louis. “We never had that before. Sex discrimination was not prohibited in the health-care system.”

This new ruling takes that prohibition one step further. While HHS has tentatively interpreted the law to include gender identity for the past several years, and has enforced it that way, the agency’s reading was still tentative. Partly because the gender-identity interpretation is so controversial, along with other parts of the law that have to do with non-English speakers and people with disabilities, the government went through a long process of soliciting comments from the public. It got 24,875 comments in total, many from advocacy-group mass mailings. The agency’s ruling synthesizes all of that feedback into a conclusion: essentially, that gender identity is part of sex.

This isn’t the first time sex discrimination has been interpreted this way. As the ruling points out, there are many years of case law that support this reading. The Supreme Court first ruled about this issue in Pricewater Cooper v. Hopkins, a 1989 case in which a woman claimed she wasn’t promoted because of the way she expressed her gender. Other federal agencies have recently taken strong positions on this issue: U.S. Attorney General Loretta Lynch, for example, has said bathroom prohibitions that affect transgender people, like the recent North Carolina law, are discriminatory. The Departments of Justice and Education jointly issued a letter to public schools last Friday intimating they might lose federal funding or face lawsuits if they don’t accommodate transgender students’ bathroom and locker-room needs. The Department of Housing and Urban Development has also long accounted for gender-identity issues, Sepper said. So in many ways, HHS is following just following legal cues. “I don’t see HHS’s interpretation of sex discrimination as being at the vanguard, but rather following what the courts are doing,” Sepper said.

The rule changes the way “gender” is interpreted under the law.

It’s still significant, though, for several reasons. First, LGBT people experience a number of health disparities compared to heterosexual people, including lack of access to appropriate care and higher rates of depression. This offers one layer of protection against those disparities, especially when it comes to insurance coverage for transgender people, Sepper said. “Many of the problems for those folks [concern] accessing gender-transition therapy and treatment,” she said. “The rule tells us that categorical exclusion of gender-transition services is going to be discriminatory.” In other words, if a doctor deems a treatment “medically necessary,” insurers won’t be able to deny coverage just because it applies to a transgender person.

The rule also changes the way “gender” is interpreted under the law. “On the definition of gender identity, it accepts that gender is not a binary,” Sepper said. “It occurs on a spectrum, and folks can even not have a gender.” This is a fairly radical shift—it accepts that people might identify as something other than “male” or “female.”

But that change is also complicated, and it’s not clear that all health-care proviers are ready to implement it. Not all hospitals have non-discrimination policies, and even those that do may not necessarily mention gender identity and sexual orientation—a 2016 Human Rights Campaign study of 904 hospitals found that only 60 percent of them mentioned those factors. The HHS ruling also notes that a number of commenters were worried about their electronic-records systems and billing software, which typically “accommodate only binary gender billing codes (e.g., ‘male’ or ‘female’) and cannot accommodate descriptions of an enrollee’s gender identity.” Even the HealthCare.gov enrollment app only lets people identify as male or female, and might not necessarily be able to account for HHS’s new, broad interpretation of gender as non-binary.

The ruling is also significant for what it didn’t do. Sexual orientation is not explicitly protected as part of sex discrimination, for example. The agency did a bit of contortion on this count: If a gay man is denied services because of the way he expresses his gender, that might count as discrimination under the ruling, for example. But it’s unclear whether doctors are allowed to deny fertility treatment to a same-sex couple on the basis of their sexual orientation, for example. “Current law is mixed on whether existing Federal nondiscrimination laws prohibit discrimination on the basis of sexual orientation as a part of their prohibitions on sex discrimination,” the ruling says. While HHS stated that it opposes this kind of discrimination as a matter of policy, it was not willing to interpret the law to include sexual orientation protections and ended up with “a sort of half measure,” Sepper said.

“The unicorn of compromise is harder to imagine in this context.”

It also did not include an exemption for religious organizations. Catholic and Baptist hospital systems will be just as liable as secular health-care providers for gender-identity discrimination if they accept federal assistance, which virtually every hospital system in the country does. While they still have some legal routes for claiming exemptions, this particular ruling doesn’t give them any additional leeway.

This almost certainly means there will be legal challenges to come. For one thing, certain state laws might come into conflict with the federal government’s interpretation of the law: Mississippi, for example, says it’s legal for any doctor to tag himself out of treatment that violates his religious belief in people’s “immutable biological sex as objectively determined by anatomy and genetics at time of birth.” Some religiously affiliated hospitals have already been accused of gender-identity-based discrimination. Last summer, for example, a transgender woman accused Medstar Georgetown, a hospital in Washington, D.C. with a “Catholic, Jesuit identity and heritage,” of denying her access to a procedure for this reason.

Although religious groups have successfully fought for exemptions to other Obamacare requirements on sex and gender, this ruling may be more difficult to challenge. In 2014, for example, the Supreme Court ruled in favor of religious organizations in Burwell v. Hobby Lobby. The Affordable Care Act requires employers to provide insurance plans that cover certain kinds of contraceptives, but some business owners had a religious objection to a handful of these kinds of birth control, which they saw as abortifacient. “In Hobby Lobby, the justices are still chasing this unicorn of compromise where everybody is happy,” said Carolina Mala Corbin, a law professor at the University of Miami. “The religious organizations agree with whatever the compromises are, and there is still seamless provision of contraceptive services to women.” In cases having to do with gender-related medical services, though, this kind of compromise probably doesn’t exist, she said. “The unicorn is harder to imagine in the anti-gender-identity discrimination context.”

The timing of this ruling doesn’t seem to be a coincidence. HHS has stepped in line behind the Justice Department and other agencies during a time of immense backlash to transgender discrimination in North Carolina and elsewhere. As a result, it was able to announce this ruling quietly and move on.

But the reach of HHS is huge, and the ruling carries symbolic import, as well. “It’s significant that the federal government is now saying, ‘Listen, we are not going to give taxpayer money to organizations that discriminate based on gender identity,’” said Corbin. That this news was hardly noted shows just how strong the administrations’ push to support transgender rights really is. All at once, the government is changing the way it interprets the law on gender and discrimination. It’s a relatively new area of civil-rights law, but soon enough, it might just be part of the status quo.