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Business Litigation

​Requirements for a Preliminary Injunction in Federal Court

June 24, 2020

Sometimes, when an individual or business files a federal lawsuit, they are not seeking compensation for a harm that has already occurred. They, instead, might ask the court to stop the defendant from actions that create additional or ongoing harm. And monetary damages might not resolve the plaintiff’s injuries.

A court may order injunctive relief prohibiting one or more parties from taking certain actions, usually on penalty of contempt of court. A court can issue an injunction at the end of a case, such as after a trial or a settlement agreement. But if a plaintiff wants to restrain the defendant’s actions while the case is still pending, they can seek a preliminary injunction. Federal law sets a high standard of proof for a preliminary injunction because it restrains a defendant’s actions before they have had a full opportunity to defend themselves against the lawsuit.

Legal Background of Preliminary Injunctions

Rule 65 of the Federal Rules of Civil Procedure governs injunctions and restraining orders. It sets specific requirements for two types of orders that courts may issue before a full trial on the merits: preliminary injunctions and temporary restraining orders (TROs).

If a court grants either type of order, Rule 65 requires the court to include the following information:

  • The reason(s) for issuing the order;
  • The specific terms of the order; and
  • The act(s) enjoined, restrained, or required, providing a reasonable amount of detail.

Preliminary Injunctions vs. Temporary Restraining Orders


A court cannot grant a preliminary injunction without notice to the other party and a hearing. A preliminary injunction lasts until a further order of the court, which could happen while the case is still ongoing, or after a trial on the merits. This could be months, or even years.

A plaintiff may obtain a TRO without notice to the defendant if the plaintiff meets strict requirements set by Rule 65, including a notarized statement detailing the need for immediate action. If the court grants a TRO under these circumstances, it will be in force for a maximum of 14 days. The court can extend its duration only for good cause.

Balancing Test for Preliminary Injunctions

Since a preliminary injunction can restrain a party’s actions for a long period of time, the U.S. Supreme Court has set a high burden of proof for a plaintiff seeking an injunction. The Court identified a four-part balancing test in Winter v. Natural Resources Defense Council, 555 U.S. 7 (2008).

1. Likelihood of Success on the Merits

First, a party seeking a preliminary injunction in a federal lawsuit must demonstrate that they are likely to succeed on the merits of their underlying cause of action. In Winter, the plaintiff sought a preliminary injunction to prevent the U.S. Navy from using sonar in certain training exercises because of the harm that it could cause to marine mammals. The plaintiff based its lawsuit on the National Environmental Policy Act of 1969. The Court held that a likelihood of success is the correct standard, rather than a mere possibility of success.

2. Likelihood of Irreparable Harm

The plaintiff must next establish that irreparable harm is likely if the court does not grant the preliminary injunction. This requires evidence of “a real and immediate threat of future injury by the defendant.” City of Los Angeles v. Lyons, 461 U.S. 95, 107 n. 8 (1983).

The Court in Winter rejected the finding by the Ninth Circuit Court of Appeals that, once a plaintiff establishes a likelihood of success on the merits, they must prove only a possibility of irreparable harm. The risk or danger must be something more definite.

3. Balance of Equities and Hardships

Once the plaintiff has established that they are likely to succeed on the merits, and that irreparable harm is likely to occur without an injunction, they must show that the balance of both equities and hardships is in their favor. This requires more than just weighing the pros and cons of the proposed preliminary injunction. In a general sense, “equities” refers to the plaintiff’s interest in obtaining an injunction, and “hardships” refers to the burden that an injunction would place on the defendant.

In Winter, the Supreme Court held that the Ninth Circuit erred in holding that the plaintiff’s interest in protecting marine wildlife outweighed the burden on the Navy’s ability to conduct training exercises. It ruled that the appellate court failed to consider warnings from Navy officials about the harm to the overall effectiveness of certain Navy programs.

4. Public Interest

Finally, the plaintiff must show that a preliminary injunction would be in the public interest. This is often a highly subjective standard, but courts can sometimes look at the statute at issue for guidance. In Amoco Production v. Village of Gambell, for example, the Supreme Court determined that the public interest promoted by the Alaska National Interest Lands Conservation Act was “to protect Alaskan subsistence resources from unnecessary destruction,” rather than preventing the actions that the plaintiff sought to enjoin. 480 U.S. 531, 544 (1987).

The Court did not have direct statutory guidance in Winter. It found that the public interest “in effective, realistic training of [the Navy’s] sailors” outweighed the interests that the plaintiff wanted to protect. Winter, 129 S.Ct. at 376.