Congress in 1932 to pass the Norris-LaGuardia Act, which imposed so many procedural and substantive limits on the federal courts' power to issue injunctions that it effectively prohibited federal court from issuing injunctions in cases arising out of labor disputes. A number of states followed suit and enacted "Little Norris-LaGuardia Acts" that imposed similar limitations on state courts' powers. The courts have since recognized a limited exception to the Norris-LaGuardia Act's strict limitations in those cases in which a party seeks injunctive relief to enforce the grievance arbitration provisions of a collective bargaining agreement. Second, injunctions were crucial to the second half of the twentieth century in the desegregation of American schools. Federal courts gave injunctions that carried out the command of Brown v Board of Education to integrate public schools in the United States, and at times courts took over the management of public schools in order to ensure compliance. (An injunction that puts a court in the position of taking over and administering an institution—such as a school, a prison, or a hospital—is often called a "structural injunction".) Injunctions remain widely used to require government officials to comply with the Constitution, and they are also frequently used in private law disputes about intellectual property, real property, and contracts. Many state and federal statutes, including environmental statutes, civil rights statutes and employment-discrimination statutes, are enforced with injunctions. Forms Injunctions in the United States tend to come in three main forms, temporary injunctions, preliminary injunctions and permanent injunctions. For both temporary restraining orders and preliminary injunctions, the goal is usually to preserve the status quo until the court is able to decide the case. Temporary restraining orders A special kind of injunction that may be issued before trial is called a "temporary restraining order" or TRO. A TRO may be issued without notice to the other party or a hearing. A TRO will be given only for a short period of time before a court can schedule a hearing at which the restrained person may appear and contest the order. If the TRO is contested, the court must decide whether to issue a preliminary injunction. Temporary restraining orders are often, but not exclusively, given to prevent domestic violence, stalking, sexual assault, or harassment. Preliminary injunctions Preliminary injunctions are given before trial. Because they are issued at an early stage, before the court has heard the evidence and made a decision