A couple celebrates upon hearing the Supreme Court has struck down the Defense of Marriage Act  in San Francisco, United States. (Photo by Justin Sullivan/Getty Images)

Many conservatives are upset with Wednesday's Supreme Court decision overturning the Defense of Marriage Act. For many, their anger has less to do with DOMA itself than with the fear that the decision will soon lead the Court to take more drastic action -- declaring all state marriage bans unconstitutional.

The majority opinion is based on federalism; Justice Anthony Kennedy argues that the federal government has "no legitimate purpose" in refusing to acknowledge marriages that states have made legal. "This opinion and its holding are confined to those lawful marriages," he writes. But the decision also invokes the equal protection clause of the Fourteenth Amendment, which holds that state governments cannot deprive some individuals of the protection of laws.

As Sen. Marco Rubio (R-Fla.) put it, "The sweeping language of today’s majority opinion is more troubling than the ruling itself as it points to further interference by the Court in the years to come."

In his dissent, Justice Antonin Scalia raised the same concern. "It takes real cheek for today’s majority to assure us, as it is going out the door, that a constitutional requirement to give formal recognition to same-sex marriage is not at issue here," he wrote. "The only thing that will 'confine' the Court’s holding is its sense of what it can get away with." Chief Justice John Roberts, on the other hand, accepts Kennedy's limits, saying the decision's reliance on federalism would lead the Court to uphold rather than strike down state bans on gay marriage.

Suzanna Sherry, a constitutional law professor at Vanderbilt University, sides with Scalia. She compared the decision to Sweatt v. Painter, the 1950 case in which the Supreme Court ruled that Texas did not have a "separate but equal" law school for black students. Four years later, in Brown v. Board of Education, the Court ruled that "separate but equal" was itself unconstitutional.

"I think that the DOMA case today, Windsor, is gay marriage's Sweatt v. Painter. It is the harbinger of a case that soon will strike down bans on gay marriage," she said. "And I think its partly because of the language the court used, and partly the reasoning that the court used, and partly just the development" of the Court's thinking on gay rights over time.

Kermit Roosevelt, a law professor at the University of Pennsylvania, agreed that "in the relatively near future the court will say that state marriage bans are unconstitutional." But nothing in today's decision makes that inevitable: "You could read it either way. It just all depends on what the court wants to do in the future."

Other experts put more stock in Kennedy's investment in the federalism argument.

"I think those concerns are overblown," said Stephen Vladeck, a law professor at American University. "If gay marriage bans at the state level are in trouble, as I think they are, that will be as true tomorrow as it was yesterday -- not because of Windsor, but because of the rest of the Court's equal protection jurisprudence."

Likewise, Randy Barnett of Georgetown University said the Court made clear it has no interest in overturning state marriage bans anytime soon. He notes that Lawrence v. Texas, the decision invalidating sodomy bans, did not come until 2003, when there was widespread consensus against them.

But lower courts, he predicted, might use Kennedy's decision as "ammunition" against state bans.

"While I think some lower courts are likely to use Kennedy's decision to invalidate state bans, a majority of this Court seems quite content to let this issue be decided state-by-state," he said.

One of those cases could wind its way back to the Court. But that could take years, and the political climate might be very different.