From the press release announcing the lawsuit:

The American Civil Liberties Union and ACLU of Alabama filed a lawsuit today challenging the state’s voter disenfranchisement laws and practices as unconstitutional. According to its state constitution, Alabama may deny voting rights to individuals who have been convicted of felonies involving “moral turpitude.” Although this term is not defined, the constitution clearly states that only the legislature can decide which felonies qualify under this category. In its lawsuit today, the ACLU charges that the state is disfranchising thousands of Alabamians under a much broader category of convictions than is permissible under the constitution, relying in part on an unlawful opinion issued by Alabama’s attorney general.

The complaint may be found here.