Which laws were used to support the injunction against the Pullman Strike?

The injunction issued against the leaders of the American Railway Union during the 1894 Pullman Strike was primarily based on two pieces of federal legislation:

• The Sherman Antitrust Act: Originally intended to address the predatory practices of industrial corporations, this act was utilized by the court to argue that the union’s actions constituted an illegal restraint of trade.12
• The Interstate Commerce Act: This legislation was invoked to establish the federal government's authority and responsibility to protect interstate commerce and the delivery of the U.S. postal service from obstruction.12

On July 2, 1894, circuit court judges Peter S. Grosscup and William A. Woods issued the order, which prohibited union leaders from compelling or inducing railway employees to fail in their duties and effectively barred them from communicating with their subordinates. The U.S. Supreme Court later upheld the government's use of this injunction in the case In re Debs, affirming that the federal government possessed the power to "brush away all obstructions" to interstate commerce and mail transportation.12