Opponents of gay marriage in the District of Columbia have suffered another setback in their ongoing effort to prevent a gay marriage law from being approved.

In a unanimous opinion released Tuesday, the city's Board of Elections and Ethics denied the group Stand4MarriageDC.com from putting a gay marriage question on the ballot. The proposed one-sentence initiative says, “only marriage between a man and a woman is valid and recognized in the District of Columbia.”

“We have considered all of the testimony presented to the Board and understand the desire to place this question on the ballot,” Board Chairman Errol R. Arthur said in a statement.

“However, the laws of the District of Columbia preclude us from this initiative to move forward,” he added.

The board's ruling said the initiative “would authorize discrimination prohibited under the [District's] Human Rights Act (HRA).”

The group Stand4MarriageDC.com is helmed by Bishop Harry Jackson, a minister at the Hope Christian Church in Beltsville, Maryland who formed the group after lawmakers approved a gay marriage-recognition law in the spring. The law, which went into effect on July 7 after a mandatory federal 30-day review period, recognizes legal gay marriages performed in other states and countries, effectively allowing District residents to port a marriage from a nearby state that grants gay and lesbian couples the right to marry.

Council member David Catania's gay marriage bill enjoys overwhelming support in the council and is expected to easily win approval on December 1.

Jackson and his followers initially attempted to keep the gay marriage-recognition law from taking effect. Citing the same Human Rights Act, however, the ethics board also rejected that effort.

Cleta Mitchell, an attorney for the group, told the AP that the group would appeal the ruling and called the board's decision a “mistake.”

“The people have the same rights [as the D.C. council] to make law on the same subject,” she said.