CHICAGO (CBS) — Two county clerks from downstate and a Chicago-based Catholic law firm are asking a judge for permission to defend Illinois’ gay marriage ban.

As WBBM Newsradio’s Dave Marsett reports, the Thomas More Society filed the request this past Friday on behalf of Effingham County Clerk Kerry Hirtzel and Tazewell County Clerk Christie Webb.

LISTEN: WBBM Newsradio’s Dave Marsett reports

Special assistant state’s attorneys will represent the downstate clerks, the society said.

The lawsuits seeking to overturn the state’s ban on same sex marriage were filed separately by the gay rights firm Lambda Legal and the American Civil Liberties Union back on May 30. They were filed on behalf of more than two dozen plaintiffs from Chicago, Bloomington and Marion last month. The couples say they have been together for nine years, 29 years, almost 50 years. But they say their relationships have never been treated as legitimate.

But the Thomas More Society argued in favor of the 1996 Illinois Defense of Marriage Act, noting that its sponsors said its purpose was “to preserve the traditional understanding of marriage and ensure that Illinois would not be required to recognize same-sex marriages performed in other states.”

The society also points out that state Sen. John Cullerton, now Senate President, spoke in defense of reserving marriage for heterosexuals at the time. While he opposed the act, he also said it was not necessary because: “It is very clear that today in Illinois marriage is reserved as a union between a man and a woman. That is our policy, and I personally support that. I think it should be reserved for a union of a man and a woman. There are historic, cultural, religious, and civil traditions for this, and we should continue in that tradition.”

But the plaintiffs seeking to overturn the law say it violates the equal protection clause of the Illinois constitution.

The lawsuit names Cook County Clerk David Orr as a defendant, but both Orr and county State’s Attorney Anita Alvarez said they wouldn’t defend it.

That decision prompted the Thomas More Society to request to enter the case, the society’s statement said.

The motion claims 15 of the 25 plaintiff couples were denied marriage licenses in Cook County despite living in other counties. That “raises a disturbing question” about whether the couples or their attorneys filed the suit in Cook County because they knew Orr would be sympathetic to their cause, it reads.

“When the ACLU and Lambda Legal brought plaintiffs from across the State of Illinois to sue the Cook County Clerk, this became a statewide issue affecting the duties and responsibilities of every county clerk in the State of Illinois,” said Peter Breen, the society’s executive director and legal counsel, said in a statement.

Breen previously called the legal motions filed by Alvarez an “end run” around the will of Illinois citizens and the General Assembly, which passed the ban in 1996 with broad bipartisan support.

Cook County Circuit Court Judge Sophia Hall will preside at a Tuesday morning hearing on the motion.