The Supreme Court's 5-4 decision Wednesday to overturn the Defense of Marriage Act is a monumental victory for advocates of same-sex marriage.
But what happens now that the 1996 federal law that confines marriage to a man and a woman has been declared unconstitutional?
Will federal benefits flow only to same-sex married couples living in states that recognize their unions?
What about same-sex spouses who are legally married but living in states that ban such unions?
And how will federal agencies, already with myriad rules and regulations regarding spousal eligibility for benefits, deal with the court's edict?
"Striking down DOMA is a great step forward, obviously," says Ari Ezra Waldman, legal editor at Towleroad, a widely read LGBT-oriented website, "but there will be difficult complications to work out."
The court's decision does not embrace a national constitutional right to same-sex marriage, but would make married gay couples living in states where their unions are legal eligible for federal benefits already enjoyed by married heterosexual Americans.
Those include considerations given to spouses in realms ranging from public employee benefits and bankruptcy to estate taxes and immigration.
The DOMA case decided by the high court involved a claim by a New York woman, who on the death of her legal same-sex spouse, paid $363,000 more in federal estate taxes than would have been collected from a heterosexual surviving spouse.
"Legally married couples in states that allow same-sex marriage are good to go," says Fred Sainz of the Human Rights Campaign, a gay advocacy organization. "The court's decision will be final in 25 days, and they should start seeing all the same federal rights and benefits."
"Where this becomes tricky is for the legally married couple in non-marry states," Sainz says.
Twelve states and the District of Columbia have legalized same-sex marriage; the Supreme Court on Wednesday also effectively made California the 13th state with legal same-sex marriage by rejecting a high court challenge to a lower court-ordered right.
Though one-third of all Americans now live in states and jurisdictions that allow same-sex marriage, a vast majority of states have enacted outright constitutional bans on gay marriage.
Place Of Celebration, Or Residence?
The tricky part in the fall of DOMA involves how states and federal agencies currently recognize marriage.
Some federal agencies adhere to what is known as a "place of celebration" standard. That means no matter where a couple is legally married anywhere in the world, the union is recognized for the purpose of federal benefits.
But other agencies, including the Internal Revenue Service and the Social Security Administration, hew to a "place of residence" standard. Marriage has to be recognized in the place the couple is living for them to be eligible for those federal spousal benefits.
"Every agency of government has, quite literally, a different standard for recognizing marriage," Sainz says. "They did not consult one another — and it has nothing to do with being gay or straight, they just have different standards."
Here's one example that points to the complexity to come: The Department of Defense has a "place of celebration" marriage standard for active-duty military. But the Department of Veterans Affairs has a "place of residence" standard.
While some definitions are set by regulation, others — including those used by Social Security and Veterans Affairs — are set by federal law, further complicating the DOMA rollback.
"It's a patchwork that makes no sense," Sainz says.
Role Of Obama Administration
So, how will this all be sorted out?
Both Sainz and Waldman say crucial roles can be played by both the Obama administration and Congress.
Same-sex marriage advocates predict, however, that with a Republican-dominated House, congressional action to resolve marriage definition disparities baked into law is unlikely. Congressional Democrats have written legislation that would uniformly apply a place of celebration standard, but it's unlikely to move beyond the Democratic-controlled Senate.
"A robust national debate over marriage will continue in the public square, and it is my hope that states will define marriage as the union between one man and one woman," said House Speaker John Boehner after the ruling.
So the task will fall to the Obama administration to implement the court's decision, and decide how and whether to apply a uniform, federal agency-wide marriage definition.
"There is no major legal impediment that can't be addressed," says Susan Sommer, director of constitutional litigation at Lambda Legal, the nation's oldest organization working for gay rights. "The administration through words and actions has shown a commitment to see federal equality."
Same-sex marriage advocates are looking for Obama to take some sort of executive action quickly, using the power to change federal regulations that define marriage in the realm of federal benefits.
A working group at the Justice Department's office of legal counsel is also said to have been working quietly for months in preparation for this day.
President Obama, in a statement issued after the ruling, said the following: "So we welcome today's decision, and I've directed the Attorney General to work with other members of my Cabinet to review all relevant federal statutes to ensure this decision, including its implications for Federal benefits and obligations, is implemented swiftly and smoothly. "
"The administration can and should adopt a universal regulation that marriages, for federal purposes, are recognized under a state of celebration standard," says Waldman, who is also associate director of the Institute for Information Law and Policy at New York Law School. "Administrations have had the power to do that since the New Deal."
"If someone has a problem with that, then it should be up to them to challenge the changes," he said. "It's a great day, but we have more litigation, more rule-making, and more work to do."