New Jersey must recognize same-sex marriage because partners in civil unions are being denied federal benefits in violation of the state Constitution, a judge ruled on Friday.

“Same-sex couples must be allowed to marry in order to obtain equal protection of the law under the New Jersey Constitution,” Judge Mary Jacobson said in granting summary judgment to six couples in Garden State Equality v. Dow.

In a 53-page opinion, she found the U.S. Supreme Court’s partial voiding of the Defense of Marriage Act on June 26 mandated the result, without the need for fact-finding.

Jacobson, the top judge for Mercer County, ordered state officials to begin allowing same-sex marriages by Oct. 21.

“This is at least the beginning of the end of a long struggle for civil rights,” said the plaintiffs’ lead attorney, Lawrence Lustberg of Gibbons in Newark. “We’re overwhelmingly gratified, not only because of the result of the ruling but also how careful, fair and scholarly it is.”

Gov. Chris Christie’s administration had opposed summary judgment, arguing it has not been established that New Jersey’s civil union law denies couples any federal benefits.

Christie spokesman Michael Drewniak would not say Friday whether the administration would ask for a stay of the order and Oct. 21 deadline but he signaled a stay request is likely by saying the issue will ultimately be decided by the state Supreme Court.

The governor “has always maintained that he would abide by the will of the voters on the issue of marriage equality and called for it to be on the ballot this election day,” Drewniak said. “Since the Legislature refused to allow the people to decide expeditiously, we will let the Supreme Court make this constitutional determination.”

Jacobson said recognition of same-sex marriage was necessary largely because of responses by at least six federal agencies to the U.S. Supreme Court’s ruling in June in U.S. v. Windsor, 133 S. Ct. 2675, which struck down the part of the Defense of Marriage Act that denied federal benefits to legally married same-sex couples in states that recognize same-sex marriage.

Jacobson said responding federal agencies have indicated that benefits will be conferred only to legally married couples, not to partners in civil unions, such as in New Jersey.

In 2006, the state Supreme Court declined in Lewis v. Harris to order the recognition of same-sex marriage, but directed the state to come up with a way to ensure that same-sex couples were treated equally with heterosexual couples. The ultimate result was the Civil Union Act.

But Jacobson said that as a result of Windsor, same-sex couples in New Jersey are no longer being treated as equals.

“The landscape in 2013 is markedly different from the one that existed just seven years ago when Lewis was decided,” she wrote.

Jacobson rejected the administration’s arguments that the issue was not ripe for summary judgment since at least some federal agencies have determined that partners in civil unions will not be eligible for benefits.

“By statutorily creating two distinct labels — marriage for opposite-sex couples and civil unions for same-sex couples — New Jersey civil union partners are excluded from certain federal benefits that legally married same-sex couples are able to enjoy,” Jacobson said.

“The parallel legal structures created by the New Jersey Legislature … no longer provide same-sex couples with equal access to the rights and benefits enjoyed by married heterosexual couples, violating the mandate of Lewis and the New Jersey Constitution’s equal protection guarantees,” she said.

“Because plaintiffs, and all same-sex couples in New Jersey, cannot access many federal benefits as partners in civil unions, this court holds that New Jersey’s denial of marriage to same-sex couples now violates Article 1, Paragraph 1 of the New Jersey Constitution.

“The equality demanded by Lewis v. Harris now requires that same-sex couples in New Jersey be allowed to marry.”

Christie vetoed legislation last year that would have legalized same-sex marriage, and supporters of the measure have not been able to garner enough votes for an override.

Assembly Speaker Sheila Oliver, D-Essex, a proponent of legalized same-sex marriage, said Friday: “This is a great victory for civil rights and treating everyone equally under the law. Sadly, same-sex couples were denied equal rights for too long, and Gov. Christie’s veto only prolonged their struggle unnecessarily. I hope Gov. Christie does the right thing and does not appeal. Justice has already been denied for far too long.”

At present, 13 other states and the District of Columbia recognize same-sex marriage. •