Story highlights "It's an amazingly strong decision," says leader of a group that sued

Judge: New Jersey must allow same-sex marriages starting October 21

Ruling says civil unions insufficient because they hinder federal benefits

New Jersey has allowed same-sex civil unions since 2007

Same-sex couples must be permitted to marry in New Jersey, a state judge ruled Friday, arguing that the parallel label "civil unions," which the state already allows gay couples, is illegally preventing them from getting federal benefits.

The judge ordered that same-sex marriages be allowed starting October 21. But the date could be delayed on appeal, and the office of Gov. Chris Christie indicated the case would be appealed to the New Jersey Supreme Court.

The ruling cites the U.S. Supreme Court's June rejection of part of the federal Defense of Marriage Act, a move that ensured same-sex spouses legally married in a state may receive federal benefits.

After the DOMA ruling, some federal agencies are extending benefits to legally married same-sex couples, but denying them to same-sex couples in "civil unions," Judge Mary Jacobson of Mercer County Superior Court wrote in her ruling Friday.

"If the trend of federal agencies deeming civil union partners ineligible for benefits continues, plaintiffs will suffer even more, while their opposite-sex New Jersey counterparts continue to receive federal marital benefits for no reason other than the label placed upon their relationship by the state," Jacobson wrote.

"This unequal treatment requires that New Jersey extend civil marriage to same-sex couples to satisfy the equal protection guarantees of the New Jersey Constitution," she continued.

Jacobson ruled on a lawsuit that six same-sex couples and their children, as well as gay-rights group Garden State Equality, filed against the state.

The group's executive director, Troy Stevenson, said the ruling is "amazing news."

"It's an amazingly strong decision. We're very excited," Stevenson said Friday. "We've been saying for months that we were going to win marriage equality for New Jersey, and this was a total victory."

An attorney who represented the plaintiffs also hailed the "thrilling" ruling.

"We argued that limiting lesbians and gay men to civil union is unfair and unconstitutional, and now the court has agreed," said Hayley Gorenberg, deputy legal director of Lambda Legal, a gay rights organization.

New Jersey has recognized civil unions between same-sex couples since 2007, after the New Jersey Supreme Court ruled that the state must allow same-sex couples all the rights and benefits of marriage. As far as state rights and benefits went, civil unions and marriages differed only in label, Jacobson noted.

Friday's ruling came more than a year after Christie vetoed a bill that would have legalized same-sex marriage in the state.

On Friday afternoon, Christie's office said it had wanted the "issue of marriage equality" to be on the ballot this November, but said the Legislature scuttled the effort. It also indicated that Jacobson's ruling would be appealed.

"Since the Legislature refused to allow the people to decide expeditiously, we will let the Supreme Court make this constitutional determination," read a Friday statement from Christie's office, which later clarified that it meant the state's high court.

The New Jersey attorney general's office, which was one of the suit's defendants, deferred CNN's questions about Friday's ruling to the governor's office.

New Jersey is one of four states that offer civil unions, but not marriage, to same-sex couples. The others are Colorado, Hawaii and Illinois.

Same-sex marriage is legal in 13 U.S states and the District of Columbia: California, Connecticut, Delaware, Iowa, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New York, Rhode Island, Vermont and Washington.

Same-sex marriage is banned in every state not mentioned above, except for New Mexico, which has no laws banning or allowing it.