The United Mine Workers (D) and the Southern Labor Union were in a dispute over representation of coal miners. Tennessee Consolidated Coal Company closed a mine where over 100 employees belonged to D's union. A wholly owned subsidiary of the Tennessee Consolidated Coal Company hired Gibbs (P) to open a new mine with members of the Southern Labor Union and to haul the coal from the mine to a railroad loading point. D's local members prevented the opening of the mine by force. P lost his job and the hauling contract. P soon began to lose other trucking contracts and mine leases he held in the nearby area. P claimed that his business losses were the result of D's intentional interference and a concerted union plan against him. P filed suit in district court for violation of Section 303 of the Labor Management Relations Act. P claimed that D’s actions were a secondary boycott. P also included a state law claim, based on pendent jurisdiction, for the unlawful conspiracy and unlawful boycott aimed at him and to maliciously, wantonly, and willfully interfere with his contract employment and his contract of haulage. The jury ruled for P on his allegations. On a motion by D, the trial court set aside the state claim award of damages based on the haulage contract and the federal claim and upheld the state law claim for interference with the employment contract. The court of appeals affirmed that decision. The Supreme Court granted review.