Pennsylvania's ban on gay marriage has been overturned by a federal judge in a decision that makes same-sex matrimony legal throughout the Northeast.

U.S. District Judge John E. Jones III's decision Tuesday is a victory for 11 couples, a widow and one of the couples' two teenage daughters who filed the first challenge to the law.

Gov. Tom Corbett's office had defended the law after Attorney General Kathleen Kane called it unconstitutional and refused to defend it.

"This is an historic day," Kane said of Tuesday's ruling. "More importantly, today brings justice to Pennsylvanians who have suffered from unequal protection under the law because of their sexual orientation. When state-sponsored inequality exists, citizens are deprived of the full protections that the Constitution guarantees."

Pa. Rep. Brian Sims, a Philadelphia Democrat and the first openly gay person elected to Pennsylvania’s General Assembly, also praised the judge's ruling.

"I'm proud to live in a state where I am one step closer to being an equal citizen," Sims said in a prepared statement. "And I am empowered to ensure that we continue the effort to bring equality in the form of an LGBT-inclusive non-discrimination law to the Commonwealth."

The Pennsylvania Family Institute spoke out against the ruling, stating that children have a right to a mother and a father.

"This decision tosses aside not just the definition of marriage recognized in law by an overwhelming majority of the people’s representatives, but the definition that has been in place in Pennsylvania since our commonwealth's founding more than two centuries ago," said Michael Geer, PFI's president.

Pennsylvania was the last remaining state in the Northeast to outlaw gay marriage.

Lawyers for the plaintiffs said the law inflicts harm on same-sex couples and their children by depriving them of the legal protections and tax benefits afforded to married couples.

An appeal to the 3rd U.S. Circuit Court of Appeals is likely.