Missouri v. United States

(1) Whether federal courts can second-guess a state"s "reason" for exercising 10th Amendment authority; (2) whether the federal Constitution prohibits states from exercising 10th Amendment authority when motivated by a concern that a federal statute is unconstitutional; and (3) whether a state official is a proper defendant under Ex parte Young simply because the official is regulated by a statute, or instead the official also needs to possess authority to enforce the challenged law.