A judge has approved the request of two Illinois county clerks to intervene in a lawsuit challenging the constitutionality of the state's gay marriage ban.

The Thomas More Society on Friday filed a request to intervene on behalf of Tazewell County Clerk Christine Webb and Effingham County Clerk Kerry Hirtzel.

Webb and Hirtzel moved to defend the ban because Cook County State's Attorney Anita Alvarez and Attorney General Lisa Madigan have said they disagree with the law and won't defend it. Cook County Clerk David Orr, who is named in the suit, also applauded the legal challenge.

Because Webb and Hirtzel are the “keepers of marriage licenses” they have an interest in ensuring that the law is applied uniformly across the state, explained Peter Breen, executive director of The Thomas More Society.

“[W]e believe we have very good arguments to prevail because of the large body of case law that goes our way on it,” Breen told the AP. “We had notified clerks that we believe they have … a strong interest in intervening.”

Webb, a Democrat, said she held no position on gay marriage.

(Related: Illinois gay marriage lawsuits combined.)