Wigglesworth v. Teamsters Local Union No. 592

Wigglesworth (plaintiff) sued Teamsters Local 592 (defendant) for denying his free speech rights at union meetings under a federal statute. Months later, at an unrelated press conference, Wigglesworth linked the union to the Mafia and accused it of fixing elections; the Teamsters then counterclaimed for defamation based on those statements, and Wigglesworth moved to dismiss the counterclaim for lack of subject-matter jurisdiction, since the parties were not diverse and jurisdiction rested solely on the federal free-speech statute.

Whether a counterclaim for defamatory statements made by the plaintiff, but unrelated to the events underlying the original complaint, is a compulsory counterclaim that the court may hear without independent jurisdiction.