Three gay couples, two of them lesbian, are planning to file a federal lawsuit challenging South Dakota's ban on gay marriage.

On Saturday, Minnesota Mayor Betsy Hodges will preside over the wedding of Nancy Robrahn, 68, and Jennie Rosenkranz, 72, of Rapid City. The women have been together 27 years.

Lawmakers in 1996 approved a law prohibiting same sex couples from marrying. A decade later, voters approved a constitutional amendment reinforcing the law.

The Pennington County clerk in Rapid City denied the women a South Dakota marriage license. Following their big day, the women plan to ask the clerk for a legal name change.

The two other couples are two men who plan on marrying soon in Iowa and a lesbian couple who married in Connecticut.

Attorney General Marty Jackley, a Republican, has already said that he will defend the ban in court.

β€œIt is the statutory responsibility of the attorney general to defend both our state constitution and statutory laws, which I intend to do if a lawsuit is filed,” Jackley told the AP.

According to the Human Rights Campaign (HRC), only four states remain without an active lawsuit challenging marriage equality bans. Once the South Dakota case is filed, the remaining states will be Alaska, Montana and North Dakota.