WASHINGTON — Supporters of same-sex marriage burst into cheers, wept openly and chanted “DOMA is Dead” outside the Supreme Court as word reached them that the justices had struck down the federal law defining marriage as a union between a man and a woman.

Some in the crowd hugged and others jumped up and down just after 10 a.m. EDT Wednesday when the decision was announced inside. Many were on their cell phones monitoring Twitter, news sites and blogs for the outcome. There were cheers as runners came down the steps with the ruling in hand and turned them over to reporters who quickly flipped through the pages.

Sarah Prager, 26, cried and shook, and hugged a stranger. Prager, who married her wife in Massachusetts in 2011, said she was in shock. “Oh that’s so good. It’s just really good,” she said.

“I didn’t expect DOMA to be struck down,” Prager said through tears. She referred to the Defense of Marriage Act, signed into law by President Bill Clinton in 1996. Gay rights activists had argued that the law improperly denied same-sex spouses the federal benefits that heterosexual couples are granted, and the justices agreed.

Inside, the reaction was subdued.

Many of the spectators had stood in line for hours to get a seat in the packed courtroom, some even camping out overnight. Before the justices took the bench, the crowd was admonished to stay silent, and they kept quiet. As Justice Anthony Kennedy read through a summary of the decision, it became clear that the court was throwing out the federal law, and a few smiles broke out across the audience. One relieved-looking lawyer blinked back her tears.

Justice Antonin Scalia followed with his own scalding dissent, ridiculing justices in the majority for what he termed “self-aggrandizement” and demonization of anyone who opposed gay marriage as an “enemy of human decency.” The other justices mostly stared ahead as he spoke.

As soon as Scalia finished, Chief Justice John Roberts announced that Scalia would be reading again, announcing the majority opinion in an unrelated case.

“I’m sorry about that — but this is shorter,” Scalia said quickly, to laughter throughout the room, before launching into a case involving a Massachusetts extortion conviction obviously of less intense interest to the crowd.

Lastly, Roberts read the court’s second gay marriage decision, a narrow ruling overturning a California proposition that banned same-sex marriage. It allows the marriages to resume there but doesn’t affect other states.

The expectant mood inside quickly deflated under the legalistic wording of the California decision. But when the plaintiffs in that case walked down the court’s marble steps with their lawyer afterward they were met with chants of “Thank you” and “USA.”

The crowd outside filled the sidewalk and spilled across the street. The vast majority were champions of gay marriage, though there was at least one person who held a sign in favor of traditional marriage. Much of the crowd waved American flags and rainbow flags and carried signs including “I (heart) my wife” and “Equality is an American value!” One man carried a closet door that towered above his head and said in part: “No more shut doors.”

Lawyer David Boies, who joined with Ted Olson in urging the court to overturn Proposition 8, said outside the court that the country is closer to “true equality.”

“Our plaintiffs now can go back to California and together with every other citizen of California marry the person they love,” Boies told reporters.

Both couples who had challenged the law said it was a good day. Sandy Stier, who held hands with her partner Kris Perry, said she was thankful the justices will let them marry, “but that’s not enough,” she said, “It’s got to go nationwide.”

Paul Katami, another plaintiff in the case, stood before reporters outside the court and became choked up as he looked at his partner, Jeff Zarrillo.

“Today I finally get to look at the man that I love and finally say: Will you please marry me?”

The pair kissed.