Three Republican lawmakers filed a motion to intervene Monday to defend against a New Jersey lawsuit to win gay marriage.

Senators Gerald Cardinale and Anthony R. Bucco, along with Assemblyman Michael Patrick Carroll, are being represented by the Christian-based group Alliance Defense Fund (ADF).

Gay rights group Lambda Legal filed the suit earlier in the month after New Jersey senators killed a gay marriage bill in January. The defeat means that the Legislature isn't likely to revisit the issue over the next four years as Governor Chris Christie, a Republican who took the helm in January, does not support giving gay couples the right to marry.

In Lewis v. Harris, the New Jersey Supreme Court unanimously agreed that it is unconstitutional to deny gay and lesbian couples the rights granted to married heterosexual couples and ordered the Legislature to remedy the situation. Lawmakers responded with a civil unions law.

Lambda Legal is representing six gay and lesbian couples plus the surviving spouse from a seventh in its challenge. The lawsuit claims civil unions are not equal to marriage.

“There's more to marriage than just any two people in a committed relationship,” ADF Senior Legal Counsel Austin R. Nimocks said in a statement. “At this time in history, we should be strengthening marriage, not tearing it down. Instead, activists are seeking to redefine marriage for all New Jersey citizens by resurrecting an already-resolved, three-year-old lawsuit with the goal of forcing legislators to redefine marriage against their will.”

“This renewed attack utterly dispels the myth that civil unions will appease such activists,” he added. “Instead, they seek to use them as a legal springboard to redefine marriage.”

Plaintiff's lawyers, however, argue that the Legislature has failed to meet the New Jersey Supreme Court's order.

“Civil unions are a failed legislative experiment in providing equality in New Jersey,” Hayley Gorenberg, deputy legal director of Lambda Legal, said, “Marriage equality is the only solution.”

All three lawmakers have publicly said they oppose giving gay couples the right to marry.