A New Jersey judge on Friday ruled the state must begin issuing marriage licenses to same-sex couples within a month.

New Jersey had previously allowed gay couples to enter civil unions. Gov. Chris Christie (R) opposes same-sex marriage and his administration is expected to contest the ruling, according to The Associated Press.

Christie’s office did not immediately respond to a request for comment.

Christie has said the issue should go before voters on a referendum.

Last year, he issued a conditional veto of a gay-marriage bill passed by the state legislature. He advocated instead for hiring an overseer to make sure gay couples in civil unions received the same protection as married couples.

However, Judge Mary Jacobson ruled Friday that the state must begin allowing same-sex couples to marry by Oct. 21.

“Same-sex couples must be allowed to marry in order to obtain equal protection of the law under the New Jersey Constitution,” the ruling stated.

Before the ruling, 13 states and Washington, D.C., allowed same-sex marriage. New Mexico has started issuing marriage licenses to same-sex couples in parts of the state as well.

In a 2006 decision, the New Jersey Supreme Court ruled gay couples were entitled to the same rights as heterosexual couples, and gave the state one of two options.

The first would have allowed gay marriage. The second — which New Jersey ultimately adopted — allowed gay couples to enter civil unions that would hold the full protection of married couples.

In light of the U.S. Supreme Court ruling earlier this year, the judge ruled there is no way to continue to extend all the benefits to gay couples without allowing them to marry.

In June, the U.S. Supreme Court ruled the federal Defense of Marriage Act unconstitutional. The federal government began recognizing same-sex marriage from states that allow it and extending benefits to those couples.

However, those benefits do not extend to civil unions in New Jersey, making them unequal and paving the way for gay marriage, the court ruled.