The Obama administration on Friday clarified that health insurance companies will not be able to deny coverage to same-sex spouses if those same benefits are offered to other couples.
The Department of Health and Human Services said the nationwide rule would go into effect next year.
The department noted that married same-sex couples are treated equally when receiving financial assistance under the new exchanges, regardless of where those couples live.
The Obama administration has already taken a number of regulator steps to expand rights to same-sex couples after a Supreme Court ruling last year that struck down a portion of the Defense of Marriage Act.
Currently, 17 states and the District of Columbia allow gay marriage. Courts in a number of others states have struck down bans pending appeal.