Nine couples are expected to file a lawsuit Tuesday challenging Colorado's ban on gay marriage.

According to FOX31 Denver, the law firm Reilly Pozner will discuss a lawsuit involving “nine Colorado couples, four of whom are legally married” during a press conference on Tuesday.

The couples, five of whom are lesbian, will “explain recent events that on Tuesday morning led them to file a precedent-setting civil rights lawsuit against the State of Colorado,” the law firm stated in an announcement.

A majority (56%) of Colorado voters in 2006 approved Amendment 43, which defines marriage as a heterosexual union.

“Essentially this is tearing down the remaining roadblocks to gay marriage,” an unnamed source is quoted as saying. “Opponents of gay marriage have lost the overall debate, and this is kind of like finishing it off.”

Colorado last year approved a law recognizing gay couples with civil unions.