Bartholet V. Reishauer A.G‪.‬

EASTERBROOK, Circuit Judge. Emil Bartholet's case summons up a doctrine only a Judge could love. Usually the plaintiff is master of his pleadings. The complaint stakes out a claim, and the allegations of the complaint determine whether the claim arises under state or federal law. See Christianson v. Colt Industries Operating Corp., 486 U.S. 800, 100 L. Ed. 2d 811, 108 S. Ct. 2166, 7 U.S.P.Q.2D (BNA) 1109 (1988). If the complaint invokes state law, and the defendant believes that federal law supplies a defense, the court in which the plaintiff files the suit will determine the validity of the defense. When the parties are citizens of the same state, the process is simple. Plaintiff picks a theory (state or federal); the theory prescribes the appropriate court, which decides the case (including the defenses).