The American Civil Liberties Union and the ACLU of Missouri, along with the MacArthur Justice Center, and the law firm of Orrick, Herrington & Sutcliffe LLP, filed a class action lawsuit against the State of Missouri over its public defender office’s inability to provide adequate defense to poor people accused of crimes across the state, as required under the U.S. and Missouri Constitutions.

The American Civil Liberties Union and the ACLU of Missouri have filed a lawsuit in state court on behalf of six same-sex couples who are seeking recognition for their legal out-of-state marriages. The lawsuit does not seek a repeal of Missouri's ban on marriage for same-sex couples within the state.

The American Civil Liberties Union filed a request for precautionary measures with the Organization of American States' Inter-American Commission on Human Rights showing that the execution of John Winfield, scheduled for June 18, 2014 in the state of Missouri, will cause irreparable harm should it go forward. The ACLU asks that the executions be stayed until the IACHR can review and rule on the ACLU's petition that alleges Mr. Winfield's death sentence violates international law. On June 6, 2014, the IACHR granted ACLU request for precautionary measures against the United States and requested that "the Government of the United States to abstain from executing John Winfield until the IACHR has ruled on the merits of the individual petition filed on his behalf."

The American Civil Liberties Union filed a petition with the Organization of American States' Inter-American Commission on Human Rights showing that the upcoming executions by lethal injection in Missouri and Oklahoma will violate international law against cruel and unusual punishment, should they go forward. The ACLU asks that the executions be stopped until the IACHR can conduct independent investigations of the two cases.