To get a preliminary injunction, a party must show that they will suffer irreparable harm unless the injunction is issued. Preliminary injunctions may only be issued after a hearing. When determining whether to grant preliminary injunctions, judges consider the extent of the irreparable harm, each party's likelihood of prevailing at trial, and any other public or private interests implicated by the injunction. Parties may appeal the judge's decisions on whether to award a preliminary injunction.
In Winter v. Natural Resources Defense Council, Inc, 555 U.S. 7 (2008), the Supreme Court described the balancing test for whether a preliminary injunction is appropriate. A court needs to examine whether the plaintiff is likely to succeed on the merits, whether the plaintiff is likely to suffer irreparable harm without the injunction, whether the balance of equities and hardships is in the plaintiff's favor, and whether an injunction is in the public interest.