Union Pacific Railroad Company filed two merger applications with the Interstate Commerce Commission (ICC) (defendant). Several competing railroads, including the Missouri-Kansas-Texas Railroad Company (MKT) and the Denver and Rio Grande Western Railroad Company (DRGW) opposed the mergers. In the alternative MKT and DRGW sought the right to use the track of the consolidated carrier if the ICC approved the merger applications. Both MKT and DRGW proposed to employ their own crews on the new routes. The ICC approved the merger applications and granted MKT and DRGW’s applications for trackage rights. The Brotherhood of Locomotive Engineers (BLE) (plaintiff) filed a Petition for Clarification. BLE argued the ICC had no jurisdiction to approve MKT or DRGW’s proposals to provide their own crews because crewing procedures involved labor issues. The ICC denied the petition on May 18, 1983. BLE and the United Transportation Union filed petitions for reconsideration. The ICC denied the petitions on October 25, 1983. BLE thereafter petitioned for judicial review of both the May 18 and October 25 orders. The court of appeals vacated both orders. ICC petitioned for certiorari.