Saint Louis, Mo. — Oral arguments will begin next week in a case representing the first serious legal challenge to Missouri’s ban on same-sex marriages. The American Civil Liberties Union of Missouri will present oral arguments on Thursday, Sept. 25 on behalf of eight same-sex couples who were married legally elsewhere in the U.S.

Under current state law, marriages from other states (including marriages between first cousins) are legally valid in Missouri as long as the union was legal in the state in which it took place. But  Missouri does not recognize the marriage of a same-sex couple in any U.S. state, regardless of legality, a violation of due process and equal protection, according to ACLU attorneys. The lawsuit comes fresh on the heels of a study funded by PROMO, the state’s largest LGBT advocacy organization, on the economic impact of gay marriage prohibitions.

The lawsuit does not challenge the state’s outright constitutional ban on same-sex marriages, and any ruling could be relatively narrow — potentially forcing Missouri to recognize out-of-state same-sex unions but doing nothing to overturn the constitutional amendment prohibiting them within the state.

The lawsuit includes a total of eight couples, including a firefighter from Jefferson City and her partner who is not eligible for spousal benefits and an elderly couple married in 2009 in Iowa after 30 years, Janice Barrier and Sherie Schild. Schild and Barrier have both been diagnosed with cancer and, because the state does not recognize their marriage, they have no legal right to make medical decisions on behalf of one another.

Judge J. Dale Youngs of the 16th Circuit Court of Jackson County will hear arguments beginning at 9:30 next Thursday in the case. Missouri is one of about 30 states with a constitutional ban on same-sex marriage. Every state with a gay marriage ban is currently being sued by groups looking to reverse the law, and since the Supreme Court’s landmark ruling in the United States v Windsor case, same-sex marriage bans have been overturned by court rulings across the country. 19 states now have legally recognized same-sex unions and another 12 states have had same-sex bans overturned by courts and are now engaged in appeals.

In Missouri, the ACLU’s case is not the only one fighting the state’s ban. In St. Louis, Mayor Francis Slay issued a small number of marriage licenses to same-sex couples in direct conflict with the state’s ban. Slay’s plan was to spark a legal battle — which he has — with the state over whether Missouri can legally prohibit same-sex marriage. Slay’s case directly challenges Missouri’s constitutional ban and could be heard in court before Christmas.

Attorney General Chris Koster told reporters at the time that he did not support the state’s ban on same-sex marriage, but that as the state’s legal representative in court, he was obligated to defend Missouri law.