The new challenge to the state's ban on gay marriage comes two weeks after a federal judge ruled Ohio must recognize marriages contracted legally in other states. U.S. District Judge Timothy Black stayed his decision.
Jennifer Branch, whose law partner was the lead lawyer in the earlier litigation, filed the lawsuit on behalf of six couples living in the Cincinnati area. The lead plaintiffs are Michelle Gibson and Deborah Meem, both professors at the University of Cincinnati who have been together for almost 20 years.
Branch said in court papers the lawsuit is critical for Gibson and Meem because Gibson suffers from multiple sclerosis.
"Because of Michelle's illness, it is important that their relationship be legally recognized very soon," Branch said in court papers.
The lawsuit says same-sex couples in Ohio are denied thousands of legal benefits available to the married under state and federal law.
"This is unfair, unjust and a complete denial of the dignity to which same-sex couples are entitled,” it says.
Seventeen states and the District of Columbia now recognize same-sex marriage. Ohio amended its constitution in 2004 to define marriage as being between a man and woman.