LGBT people have protection against housing discrimination under the Federal Fair Housing Act, a federal judge ruled for the first time last week.

The federal law prevents landlords from refusing to rent or sell housing to anyone based on “sex, familial status, or national origin,” but does not explicitly mention sexual orientation or gender identity, according to the Washington Post.

A federal judge in Colorado issued the ruling Wednesday in a case brought by a one a transgender woman and her wife. The couple said their efforts to rent a Boulder, CO, town home was rejected by a landlord who gave as a reason their “unique relationship,” the Washington Post reports.

In his opinion, U.S. District Judge Raymond P. Moore said the refusal to rent to the couple based on their perceived failure to conform to “stereotype norms” of a traditional household was discrimination of sex under the federal law.

The federal Fair Housing Act, passed in 1968, mentions sex as prohibitive discriminating factors but does not mention sexual orientation and gender identity. However, discrimination against a LGBT person may be covered by the act if it is based on non-conformity with gender stereotypes, according to the U.S. Department of Housing and Urban Development.

“For example, if a housing provider refuses to rent to an LGBT person because he believes the person acts in a manner that does not conform to his notion of how a person of a particular sex should act, the person may pursue the matter as a violation of the Fair Housing Act’s prohibition of sex,” HUD writes on its LGBT rights page.

Last week’s case was the first time the clause was used to prove discrimination based on stereotypes, according to media reports.

Nearly 50 years after its passage, the Fair Housing Act has helped prevent housing discrimination, but it has had a modest impact on homeownership rates for minorities, according to a recent study on the landmark law’s impact.