A court order that orders a party to do or refrain from doing a certain act (or acts) as opposed to a money judgment. For example: An injunction might be obtained to prevent a copyright infringer from reprinting copyrighted materials; in divorces there are frequently mutual restraining orders (a form of injunction) requiring both parties to leave another alone; A court order which restrains one of the parties to a suit in equity from doing or permitting others who are under his control to do an act which is unjust to the other party; If a party has threatened to remove marital property, or has threatened to kidnap, a court might prohibit the party from touching any marital property or removing the child from the county.
Emergency injunctions that are in effect only a short time are called temporary restraining orders. Courts can also issue preliminary injunctions to take effect immediately and effective until a decision is made on a permanent injunction, which can stay in effect indefinitely or until certain conditions are met.
An injunction clearly forbids a certain type of conduct. This is why Federal Rule of Civil Procedure 65(d) 'requires the language of injunctions to be reasonably clear so that ordinary persons will know precisely what action is proscribed ,' and why 'all ambiguities are resolved in favor of the person subject to the injunction.' United States v. Holtzman, 762 F.2d 720, 726 (9th Cir.'85) (emphasis added). Cf. Movie Systems, Inc. v. MAD Minneapolis Audio Distrib., 717 F.2d 427, 432 (8th Cir.'83) (injunction was specific enough to give 'explicit notice of precisely what conduct is forbidden').
A district court can enforce its injunction when: (1) it is based on an interpretation of federal law, (2) the federal law's purpose and language (in light of controlling federal decisions including the injunction) is clear, and (3) the effect of the state program being implemented hampers the exercise of that federal law. It is well settled that courts have wide discretion to order the relief necessary to effectuate their judgments. See 28 U.S.C. Sec. 1651 (authorizing courts to 'issue all writs necessary or appropriate in aid of their respective jurisdictions'); Swann v. Charlotte-Mecklenburg Board of Education, 402 U.S. 1, 15-16 (1971) ('Once a right and a violation have been shown, the scope of a district court's equitable powers to remedy past wrongs is broad, for breadth and flexibility are inherent in equitable remedies.'). It is also firmly established that a federal court which has imposed an injunction also retains the power to suspend or modify it. System Federation v. Wright, 364 U.S. 642, 646-47 (1932).
The power of a federal court to protect and enforce its judgments is unquestioned. United States v. New York Telephone Co., 434 U.S. 159, 172-73(1977). Moreover, the equitable jurisdiction of a federal court 'extends to supplemental or ancillary bills brought for the purpose of effectuating a decree of the same court.' Hamilton v. Nakai, 453 F.2d 152, 157 (9th Cir. 1972).
The power of the court to issue an order to require compliance or to enforce its judgment 'follows from the principle that a court's power to afford a remedy must be coextensive with its jurisdiction over the subject matter.' 453 F.2d at 157.
Generally, injunctions fall into that class of decisions that are immediately appealable without a final judgement having issued.