Maryland Governor Martin O'Malley on Thursday signed a gay marriage bill into law, making Maryland the eighth state to legalize such unions.

At a signing ceremony surrounded by supporters in Annapolis, O'Malley said that “the way forward is always greater respect for equal rights for all.”

“We are one Maryland and all of us at the end of the day want the same things for our children. We want them to live in a loving, caring and committed home that is protected equally under the law.”

The crowd burst into cheers when O'Malley announced, “The bill is signed.”

O'Malley announced last spring that he would include the legislation in his 2012 legislative package. He championed the bill in his annual State of the State address and at committee hearings on the issue.

After clearing its highest hurdle in the House of Delegates – where Democratic leaders last year shelved a similar bill without taking a vote – the Senate, which passed the legislation last year, gave its okay.

Opponents, however, have already begun an effort to repeal the law. On Wednesday, they announced that the State Board of Elections had approved their petition language, The Washington Post reported. The campaign to put the law up for a popular vote will be organized by the Maryland Marriage Alliance, which is supported by the National Organization for Marriage (NOM).

Nearly 56,000 valid signatures, one-third of which would need to be submitted by May 31, with the remainder by June 30, are needed to put the measure on the fall ballot.