Latrobe Steel Company (Latrobe) (plaintiff) had production and maintenance employees who were represented by United Steelworkers of America and its Local Union No. 1537 (United) (defendants). Latrobe and United were parties to a collective-bargaining agreement that contained a broad no-strike clause and an arbitration provision. United and another local union representing office workers were the certified representatives of the employees at the Latrobe plant. The office workers established a picket line outside the Latrobe building after efforts to negotiate a collective-bargaining agreement between the office workers and Latrobe failed. The United production workers refused to enter the plant because of the picket line. Latrobe brought an action in federal district court under section 301 of the Labor Management Relations Act of 1947, 29 U.S.C. § 185, seeking (1) a temporary restraining order against the refusal of the production workers to cross the picket line and (2) an order holding United and certain officers and members in civil contempt after continued refusal by the workers. The district court granted the preliminary injunction and issued a contempt order imposing a $10,000 fine payable to the United States if the production employees did not report for the next shift, and an additional $10,000 payable to the United States for each subsequent day that United failed to comply with the injunction. United appealed, arguing that the district court had no jurisdiction to issue the preliminary injunction and that the civil-contempt order should therefore be vacated.