On Friday the Defense Department decided to allow military chaplains to perform same-sex unions, whether on or off a military installation, but only in states that have already legally recognized gay marriage. The ruling, announced by the Pentagon’s personnel chief, follows the recent repeal of “Don’t Ask, Don’t Tell.”

“It is outrageous that only 10 days after repeal of the law against homosexuality in the Armed Forces, the Defense Department is already pushing the military further down the slippery slope,” said Tony Perkins, president of the Family Research Council, in a statement.

The Pentagon issued guidelines on the proceedings, but said military chaplains are not required to perform a ceremony if doing so goes against their religious or personal beliefs.

Military Chaplains Association’s spokesman Gary Pollitt told The Washington Post, “Regardless of the Pentagon guidance, military chaplains will still need to take cues from their religious order.”

Some members of Congress have objected to military chaplains performing same-sex unions, saying it would violate the 1996 Defense of Marriage Act.

The Pentagon also says Defense Department property may be used for private functions, including religious and other ceremonies such as same-sex unions, as long as state or local laws do not prohibit it.

Jordan Lorence, an attorney with the Alliance Defense Fund said, “This is unique in American history where you have military policy at odds with the belief system of the chaplains that they rely on.”

The Associated Press contributed to this article.