The National Guard is quietly emerging as a gay rights battleground.

Oklahoma became the fourth state this month to refuse to order its National Guard to process federal benefits applications for same-sex couples, joining Texas, Louisiana and Mississippi in setting up a potential conflict with the Obama administration and gay rights advocates.

National Guard units have a unique status, existing under the authority of their respective states and the federal government.

The American Civil Liberties Union and the American Military Partners Association, a gay service members group, launched a petition last week calling on the Pentagon to “put these states in line and enforce equal access to benefits for all military families nationwide.”

The Obama administration pledged to provide federal benefits to legally married same-sex couples after the Supreme Court struck down key parts of the Defense of Marriage Act in June.

But the four state National Guards say their state constitutions, all of which define marriage as a union only between a man and a woman, conflict with a new Pentagon rule requiring the military to treat married couples equally.

A host of other states that don’t recognize same-sex marriage — including Alabama, Kentucky, Michigan, North Carolina and Virginia — have said they will process the federal benefits, raising a question about whether the other four states’ policies are more a matter of discretion than legal obligation.

“They’re service members applying for benefits, so we give them to them,” said Lt. Col. Kirk Hilbrecht, a spokesman for the Kentucky National Guard.

Florida is still deciding whether to process benefits for same-sex couples. Maj. Gen. Emmett Titshaw Jr., who oversees the guard forces there, asked the state’s attorney general, Pam Bondi, to offer an opinion on the matter, but she declined. Bondi asked Titshaw to first clarify how the Defense Department’s directive would conflict with his duties under Florida law.

Opponents of same-sex marriage have applauded the four states for their defiance.

“What we’re seeing here is the unconscionable and immoral impulse of the federal government to force itself into state marriage policy, where it has no right to meddle,” said Bryan Fischer, director of issues analysis for the American Family Association.

The Pentagon has declined to comment on whether it is reviewing the state policies or whether the federal government can force states to process benefits applications. The White House and Justice Department did not respond to questions about whether they will challenge the noncomplying states.

‘A true Rubicon moment’

Alicia Butler’s views are unequivocal.

“I see politics here,” said Butler, whose spouse, Judith Chedville, is a member of the Texas National Guard and served in Iraq in 2003. “Points are being scored by standing up to the federal government or by going against gays. It’s really just a cheap shot.”

Butler and Chedville, who were married in California in 2008, were excited about the Supreme Court’s ruling, which made them both eligible for military benefits. “The first thing I said was that our license would be more than just a piece of paper now,” Butler recalled. “It was nothing as far as Texas was concerned.”

The noncomplying National Guard units have encouraged same-sex couples to apply for benefits at federal installations in their states.

Butler and her wife live in Austin, and they would have to drive at least 70 miles to submit paperwork at a federal facility. “It’s a slap in the face when I’m 10 minutes away from the place where I should be able to apply for something the Supreme Court says I’m entitled to,” Butler said.

Legal experts say the Obama administration could try to compel the state National Guards to comply by withholding federal funds or by taking the matter to court.

Any legal battles that arise could carry implications for states’ rights, much like the fight over Arizona’s strict 2010 immigration law, in which Justice successfully argued that the statute infringed upon the federal government’s constitutional authority to set and enforce immigration rules.

“This is a true Rubicon moment for the National Guard,” said Jonathan Turley, a constitutional law professor at George Washington University. “If the federal government can now dictate the benefits and treatment of guardsmen, there remains very little of the original state control. The only remaining residue is that they can still be called out by governors.”

Turley said he supports the Pentagon’s position but recognizes the potential for a pivotal legal battle.

State-federal tensions

The dual nature of the National Guard sometimes leads to conflicts. Governors or adjutants general oversee the forces, but the majority of their funding comes from federal coffers, and the Defense Department writes many of the policies they must follow.

The last high-profile example of a state-federal conflict over the National Guard occurred in 2005, when then-Louisiana Gov. Kathleen Babineaux Blanco refused to cede control of her state’s troops during the disorganized response to Hurricane Katrina. President George W. Bush considered invoking the 1807 Insurrection Act to take command of the forces but ultimately decided against it.

Outside of wartime and disaster responses, questions about administrative issues for the National Guard are largely unexplored territory, according to defense officials. Legal experts say that makes the benefits matter ripe for litigation.

Suzanna Sherry, a law professor at Vanderbilt University, said individual people may be more likely than the federal government to challenge the National Guard decisions. Either way, the plaintiffs could argue that federal law trumps state law or that states must recognize gay marriages registered in other states, under the DOMA ruling in United States v. Windsor.

Opponents of same-sex marriage could also mount legal challenges in states that comply with the Pentagon policy despite their constitutional bans on such unions.

“Taxpayer standing arguments,” however, have met with limited success, Turley said.

It’s too early to know how the issue will play out and whether the Obama administration will push back on the states, he added.

“It’s not clear that they have the political currency to buy into this fight,” he said. “But if they don’t, this will be a continued issue brought up with the White House.”