The Supreme Court decision may have ruled that married same-sex couples are entitled to the same federal benefits as heterosexual couples, but there remains a gap in workplace protections for many employees when it comes to one key federal benefit: the right to take time off to care for a sick spouse.

That’s because the Family Medical Leave Act, the federal law that allows employees to take 12 weeks of job-protected leave to care for a sick family member, is administered by the Labor Department, which bases eligibility on the marriage laws of an employee’s state of residence, not the state where they got married.

That means same-sex couples who wed in the District or Maryland, but live in Virginia, may not be entitled to spousal FMLA leave until the Labor Department changes the way it determines eligibility for spousal leave.

The District-based Human Rights Campaign, the nation’s largest lesbian, gay, bisexual and transgender civil rights organization, is lobbying to do just that.

“We’ve been urging [the Labor Department] to undertake rulemaking and change that so that those couples do have right to take that FMLA leave,” said Brian Moulton, the organization’s legal director.

The Labor Department’s current regulation defines a spouse as a “husband or wife as defined or recognized under state law for purposes of marriage in the state where the employee resides.”

The Human Rights Campaign is pushing for the agency to change that definition to “state of celebration” — the state where the couple gets married.

“Adoption of the ‘state of celebration’ standard ... will ensure that access to this federal benefit is consistent for all legally married same-sex couples regardless of state of residence,” wrote Allison Herwitt, legislative director of the Human Rights Campaign, in an August letter to Secretary of Labor Thomas Perez.

Fifteen states and the District of Columbia recognize same-sex marriage, and the spousal leave issue is particularly confusing when companies have employees who live in multiple states, or work and live in bordering states that have different laws regulating same-sex marriage.

“This is a headache,” Human Rights Campaign’s General Counsel Rob Falk said at a panel on LGBT law at last month’s Association of Corporate Counsel meeting. “The workforce in our area is very fluid. This gets complicated very quickly when you have a mobile workforce. Individuals may reside in one state, or move to another on temporary assignment ... We don’t have much guidance about how that’s going to work.”