Insurers can’t offer health coverage to a spouse in a traditional marriage if they don’t also make the same coverage available to spouses in same-sex marriages, the federal government announced Friday.

The change means that same-sex married couples who have been unable to buy family policies will be able to do so.

The guidance, presented in an FAQ format from the Department of Health and Human Services, applies to health plans in the group and individual markets that were not in operation before the health law and grandfathered in the federal health law. It clarifies existing federal rules, the guidance said.

Same-sex couples who were married in any of the 17 states and the District of Columbia that authorize same-sex marriage are entitled to equal access to spousal coverage, no matter where they currently live or where the policy is offered.

“It’s a big deal,” says Katie Keith, director of research at the Trimpa Group, a consultancy that works on lesbian, gay, bisexual and transgender issues. “If you identify as married, it’s hard to stomach that you can’t get family coverage.”

The new guidance, however, does not extend to couples who are in domestic partnerships or civil unions.

In February, insurers in Pennsylvania, North Carolina and elsewhere came under criticism for refusing to sell family coverage to married same-sex couples on the health insurance exchanges. North Carolina subsequently revised its policy to allow same-sex married couples to buy family plans.

At the time, the administration said it was aware some same-sex couples were having trouble buying family plans and was looking into ways to address the issue for the 2015 plan year.

Unequal access to coverage runs afoul of the health law’s prohibition against marketing practices or health insurance benefit designs that discriminate on the basis of sexual orientation, the FAQ said.

Last year, in a landmark decision, the Supreme Court struck down a key part of the federal Defense of Marriage Act that denied federal recognition of same-sex marriage.

The federal guidance requires insurers to bring their policies into compliance by Jan. 1, 2015, at the latest.