Lambda Legal Defense and the ACLU filed separate lawsuits Wednesday (May 30), seeking the right to marry for same-sex couples in Illinois.

In Darby v. Orr in the circuit court for Cook County, Lambda argues that a state law banning same-sex marriages violates the state constitution’s guarantee of due process and equal protection. The lawsuit also says the ban violates the state constitution’s prohibition against creating laws that affect just one group when a law “is or can be made” that applies generally to everyone, such as marriage laws.

In Lazro v. Orr in that same court, the ACLU made those arguments and more, saying the marriage ban law violated the right to equal protection based on sexual orientation and based on gender, as well as the right to privacy of same-sex couples.

Lambda’s lawsuit is the second marriage lawsuit the group has filed in less than two months. In April, Lambda filed a federal lawsuit in Nevada, Sevcik vs. Sandoval, arguing that the state’s denial of marriage licenses to same-sex couples violates their U.S. Constitutional right to equal protection under the 14^th Amendment. But, unlike Nevada, which bans same-sex marriage through a state constitutional amendment, Illinois bars same-sex marriage through a state law only. Lambda also led the successful lawsuit, Varnum v. Brien, in Iowa that led to a state supreme court ruling in 2009 that said the state constitution guarantees equal treatment of same-sex couples under the state’s marriage laws.

The Lambda lawsuit in Illinois involves 16 same-sex couples, including 80-year-old Korean War veteran James Darby and his companion of 48 years Patrick Bova, 73, who live in Chicago. David Orr is the Cook County Clerk, who is authorized to issue marriage licenses.

The ACLU lawsuit in Illinois involves nine same-sex couples, including Chicago police detective Tanya Lazro and her partner of 15 years, Elizabeth Matos.

The two lawsuits were apparently developed separately, but the groups are coordinating the announcement of them.

The Illinois legislature passed a law permitting same-sex couples to obtain civil union licenses and that law went into effect in June 2011. But Windy City Times, the state’s gay newspaper, has documented a number of instances in which “government entities, hospitals, organizations and employers either failed or struggled” to afford due recognition to civil unions. A bill in the state legislature seeking to repeal the same-sex marriage ban, reports Windy City, has not moved this session.

The two lawsuits in Illinois now join almost many others around the country, in state and federal courts, seeking to undo laws that block same-sex couples from equal treatment under marriage laws. In addition to Nevada, Lambda has a third marriage lawsuit, Garden State Equality v. Dow, pending in New Jersey state court, and that case includes some federal law issues. The ACLU has a lawsuit challenging the federal Defense of Marriage Act (DOMA), pending in federal court in New York. That lawsuit, Windsor v. U.S., and two by Gay & Lesbian Advocates & Defenders (GLAD), challenges Section 3 of DOMA, which bans, for any federal purpose, the recognition of a legal marriage from any state or other jurisdiction. One of the GLAD lawsuits, Gill v. OPM, is consolidated with a lawsuit from the state of Massachusetts, Commonwealth v. HHS, and is awaiting a decision from the First Circuit U.S. Court of Appeals. The other, Pedersen v. OPM, is pending in Connecticut federal district court.

And in California, a high-profile case, Perry v. Brown, challenging the Proposition 8 ban on same-sex marriages, has succeeded in federal district court and before a three-judge panel of the Ninth Circuit U.S. Court of Appeals. The panel decision has been appealed but the full circuit has not yet indicated whether it will hear the case.