The U.S. Supreme Court considered an appeal by the State of Kansas that arose from the Kansas Supreme Court's invalidation of the Kansas Sexually Violent Predator Act. The Act establishes procedures for the civil commitment of persons who, due to a "mental abnormality" or "personality disorder," are likely to engage in "predatory acts of sexual violence." The Supreme Court held that the Act's definition of "mental abnormality" satisfies substantive due process requirements. The Court further held that since the Act does not establish criminal proceedings, it does not violate the Constitution's double jeopardy prohibitions or its ban on ex post facto lawmaking. The Court's holding and its implications are discussed.