The DOL's guidance addresses one of the trickier questions to arise from the court's June decision: whether where a same-sex couple lives affects their benefits eligibility.  

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In providing its rationale for the guidance, the agency said that a rule that recognizes marriages valid in the state in which they were celebrated, regardless of the couple's state of domicile, provides "a uniform rule of recognition that can be applied with certainty by stakeholders, including employers, plan administrators, participants, and beneficiaries."

In contrast, it said, a rule for employee benefit plans based on state of domicile would raise "significant challenges" for employers that operate or have employees (or former employees) in more than one state or whose employees move to another state while entitled to benefits.

"The need for and validity of spousal elections, consents, and notices could change each time an employee, former employee, or spouse moved to a state with different marriage recognition rules," the DOL said. "The employers or plan administrators would need to continually track the state of domicile of all same-sex married employees and former employees and their spouses."

"For all of these reasons, plan administration would grow increasingly complex, administrators of employee benefit plans would have to be retrained, and systems reworked, to comply with an unprecedented and complex system that divides married employees according to their sexual orientation. In many cases, the tracking of employee and spouse domiciles would be less than perfectly accurate or timely and would result in errors or delays."

All of these problems are avoided by the adoption of a rule that recognizes marriages are valid wher they were celebrated.

The DOL said it coordinated with the Treasury Department, which oversees the IRS, as well as the Deparment of Health and Human Services in developing its stance.

"This (court's) decision represents a historic step toward equality for all American families, and I have directed the department's agency heads to ensure that they are implementing the decision in a way that provides maximum protection for workers and their families," Secretary of Labor Thomas E. Perez said in a statement.

"The department plans to issue additional guidance in the coming months as we continue to consult with the Department of Justice and other federal agencies to implement the decision," he added.

In an earlier guidance, issued in August, Perez announced that the spousal leave provisions of the Family and Medical Leave Act apply to married same-sex couples.

The FMLA entitles eligible employees of covered employers to take unpaid, job-protected leave for specified family and medical reasons, including to care for a spouse with a serious health condition.

Separately, the federal Office of Personnel Management announced in late June that same-sex spouses of federal employees and annuitants are eligible for coverage under the federal government's benefits programs.