An injunction is an equitable remedy in the form of a court order that either prohibits or compels ("enjoins" or "restrains") a party from continuing a particular activity. The party that fails to adhere to the injunction faces civil or criminal contempt of court and may have to pay damages or sanctions for failing to follow the court's order.
Basis of injunctions
At the very core of injunctive relief is a recognition that money damages can't solve every problem. An injunction may be permanent or it may be temporary. A temporary injunction (or preliminary injunction) is a provisional remedy granted to restrain activity on a temporary basis until the court can make a final decision after trial. It is usually necessary to prove the high likelihood of success upon the merits of one's case and a likelihood of irreparable harm in the absence of a preliminary injunction before such an injunction may be granted; otherwise the party may have to wait for trial to obtain a permanent injunction.
In United States law, a temporary restraining order (or TRO) may be issued on a short-term basis until the court decides whether to issue a preliminary injunction. Thus, the relationship between a TRO and a preliminary injunction is the same as the relationship between a preliminary injunction and a permanent injunction. In some cases a TRO may be granted ex parte, i.e. without informing the party to whom the TRO is directed in advance. Usually such ex parte orders are of a short term and are to prevent one's adversary from having notice of one's intentions. Such notice may allow the eventual object of the application for an injunction from doing something that would make the court's granting of an injunction fruitless, such as wasting or hiding assets as often occurs in dissolution of marriage or in the disclosing of a trade secret that had been the subject of a non-disclosure agreement.
Rationale behind injunctions
This injunctive power to restore the status quo ante; that is, to make whole again someone whose rights have been violated, is essential to the concept of fairness (equity). For example, money damages would be of scant benefit to a land owner who wished simply to prevent someone from repeatedly trespassing on his land. The ability of the landowner to use the courts to sue the trespasser for injunctive relief is often the only practical way to end the trespass (the government may or may not bring criminal trespass charges at the landowner's urging; the civil power is in the landowner's own hands). Once the order is secured, the trespasser violates it at his own peril, risking fines and imprisonment for contempt of court.
Courts may also issue mandatory injunctions, also called mandatory orders, i.e. equitable relief to compel a person to do a specific act or acts or follow a course of conduct; though in some jurisdictions courts will not issue mandatory orders that require judicial oversight to insure compliance with the judge's order.
Injunctions in U.S. labor law context
After the United States government successfully used an injunction to outlaw the Pullman boycott in 1894, employers found that they could obtain federal court injunctions to ban strikes and organizing activities of all kinds by unions. These injunctions were often extremely broad; one injunction issued by a federal court in the 1920s effectively barred the United Mine Workers of America from talking to workers who had signed yellow dog contracts with their employers.
Unable to limit what they called "government by injunction" in the courts, labor and its allies persuaded the U.S. 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 as to effectively prohibit all federal court 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.