Unless a higher court steps in and stops enforcement of the ruling, the state will have to allow same-sex couples married outside the state to change their names on official identifications and documents and obtain any other benefits of a married couple in Kentucky.
Laura Landenwich, who represents several of the plaintiffs, called Beshear's move "a political stunt designed to cull favor" for any future run for office.
"A true failure in leadership, and a waste of taxpayer dollars for the exclusive benefit of these politicians," Landenwich said.
Dawn Elliott, another attorney representing the plaintiffs, said any appeal is unlikely to be successful, no matter who argues the case for the state. "The legal analysis is the same," Elliott said.
Martin Cothran, a spokesman for The Family Foundation of Kentucky, which opposes same-sex marriage, charged Conway with "spiking the case" by not offering up a stronger defense.
Conway, who said he consulted with Beshear and state lawmakers, said he prayed over the decision.
"In the end, this issue is really larger than any single person and it's about placing people above politics," Conway said. "For those who disagree, I can only say that I am doing what I think is right."
The decision in the socially conservative state comes against the backdrop of similar rulings or actions in other states where same-sex couples have long fought for the right to marry. Kentucky's constitutional ban was approved by voters in 2004 and included the out-of-state clause.
The U.S. Supreme Court ruled in June that same-sex couples were entitled to federal benefits. Since then, a federal judge in Texas last week struck down that state's gay marriage ban but immediately delayed the implementation of his ruling pending appeals by the state. In January, the U.S. Supreme Court put a hold on a decision in Utah recognizing same-sex marriages.