"The ineligibility of same-sex couples for federal benefits is currently harming same-sex couples in New Jersey in a wide range of contexts," wrote Judge Mary C. Jacobson in her decision.
The judge said her decision would take effect Oct. 21. But Gov. Chris Christie announced late Friday he plans to appeal, which could delay the implementation, The Star-Ledger of Newark reported.
Jacobson said, for example, civil union partners who are federal employees in New Jersey currently are not eligible for marital rights under the federal pension system. New Jersey allows civil unions between same-sex couples.
She granted an emergency request by six same-sex couples supported by Garden State Equity, a gay rights group, and Lambda Legal, and ordered state officials to permit same-sex marriage beginning Oct. 21.
Her ruling that the state Constitution must allow same-sex marriage came after the U.S. Supreme Court's June decision invalidating the Defense of Marriage Act. Christie vetoed a same-sex marriage bill in 2012.
"Gov. Christie 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," spokesman Michael Drewniak said. "Since the legislature refused to allow the people to decide expeditiously, we will let the Supreme Court make this constitutional determination."
Drewniak did not say whether the governor plans to ask the courts for a hold on gay marriage during the appeal. The case is almost certain to go to the state Supreme Court.
In 2006, the state Supreme Court ruled gay couples were entitled to the same benefits as heterosexuals but said civil unions would be adequate.
Democrats hailed Friday's ruling. U.S. Sen. Robert Menendez urged Christie to let the decision stand without appeal as did Sheila Oliver, the speaker of the state Assembly, the Star-Ledger said.
"This is a great victory for civil rights and treating everyone equally under the law," Oliver said in a statement. "October 21 should be a very exciting day for many loving New Jersey couples, and I hope Governor Christie does the right thing and does not appeal."