To get a preliminary injunction, you have to satisfy four requirements the Supreme Court laid out in Winter v. Natural Resources Defense Council: a likelihood of success on the merits, a likelihood of irreparable harm without the order, a balance of equities tipping in your favor, and consistency with the public interest. You carry the burden on all four, and courts treat the relief as extraordinary rather than routine, so the evidence has to be persuasive even on an incomplete record. Procedurally, you also need to give the other side notice, appear at a hearing, and in most cases post a security bond before the order takes effect.
Likelihood of Success on the Merits
The first factor asks whether you’re likely to win the underlying case. The judge reviews your legal theories, the evidence you’ve gathered so far, and any obvious defenses to gauge whether your claim has real legs. You don’t need trial-level certainty, but you need more than a plausible theory. If the legal arguments are weak or the key facts are genuinely disputed, this factor alone can sink the motion.
Judges are reluctant to restrict a party’s conduct based on a claim that might not survive a motion to dismiss, let alone a full trial. Front-load your strongest proof: contracts, communications, expert opinions, or whatever else anchors the claim.
The Sliding Scale Variation
Several federal circuits, including the Second, Seventh, and Ninth, apply a “serious questions” variation. Under this approach, you don’t have to show probable success if you can raise serious, substantial questions about the merits and the balance of hardships tips sharply in your favor. The Ninth Circuit confirmed after Winter that the test survives, but only when the movant also demonstrates a likelihood of irreparable injury and that the injunction serves the public interest.1Ninth Circuit Court of Appeals. Alliance for the Wild Rockies v. Cottrell The sliding scale lets you trade down on the merits factor; it does not let you skip the other three.
Not every circuit recognizes this flexibility. Some read Winter as requiring a probable-success showing in all cases. If you’re filing in a circuit that hasn’t explicitly adopted the sliding scale, plan to meet the traditional standard.
Irreparable Harm
This is where most preliminary injunction motions live or die. You have to show that without the court’s intervention, you’ll suffer harm money can’t fix after trial. The classic example is demolition of a historic building: once it’s gone, no damages award rebuilds it. The same logic covers disclosure of trade secrets, destruction of natural resources, or ongoing violations of constitutional rights.
The Supreme Court made clear in Winter that a mere possibility of irreparable harm is not enough. You need to show the harm is likely, not speculative.2Justia. Winter v. Natural Resources Defense Council, Inc., 555 U.S. 7 (2008) If your losses are purely financial and can be calculated and compensated through a damages award later, courts will usually tell you to wait for trial. The reasoning is simple: the legal system already has a remedy for monetary losses, so injunctions get reserved for situations where that remedy falls short.
Timing matters too. The harm must be imminent, meaning it’s either already happening or will happen before the case reaches trial. A threat that might materialize years from now doesn’t justify emergency relief today. Judges want concrete evidence that the clock is running out, not abstract warnings.
Balance of Equities and Public Interest
Even if you’re likely to win and face irreparable harm, the court weighs what the injunction would do to the other side. The judge compares your potential losses against the burden the defendant would bear under the restriction. If complying with the order would effectively destroy the defendant’s business while your harm is significant but survivable, the balance might not tip your way.
The public interest analysis broadens the lens. In cases involving environmental regulations, public health measures, or government enforcement, the court considers how the order affects everyone else. An injunction protecting your intellectual property rights might be straightforward; one blocking a public utility or halting enforcement of a safety regulation gets far more scrutiny. Courts won’t issue an order that solves your problem while creating a bigger one for the community.
These two factors often merge in practice, especially where a government regulation is in play, but they remain formally separate inquiries and courts are expected to address both.
Prohibitory vs. Mandatory Injunctions
Most preliminary injunctions are prohibitory: they stop someone from doing something. A court might order a competitor to stop using your trademark or prevent a developer from demolishing a building during litigation. The four-factor test applies as described above.
Mandatory injunctions, which require a party to take affirmative action, face a higher bar. Courts treat them as appropriate only in extraordinary circumstances where the moving party’s case is clearly strong and the defendant’s conduct has been egregious. Ordering someone to do something before trial is a more aggressive intervention than ordering them to stand still, and judges are correspondingly more cautious. If your motion asks the court to force the other side to act, expect skepticism and prepare a stronger evidentiary showing.
How a Temporary Restraining Order Fits In
A TRO is emergency relief designed to hold things in place for days, not weeks or months. A preliminary injunction is the more durable order that carries through trial. The three differences that matter most:
- Notice. A preliminary injunction requires notice to the opposing party before the court can act. A TRO can issue without any notice at all if you show through an affidavit that waiting for notice would result in immediate and irreparable harm, and your attorney certifies in writing what efforts were made to notify the other side.3Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders
- Duration. A TRO expires no more than 14 days after entry, though the court can extend it once for another 14 days for good cause. A preliminary injunction has no built-in expiration date and lasts until the court modifies it or the case concludes.3Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders
- Hearing. TRO decisions are typically made on the papers alone. Preliminary injunctions require a hearing where both sides present arguments and evidence, including live witness testimony.
The usual sequence: file for a TRO to get immediate protection, and the court schedules a preliminary injunction hearing shortly afterward. If the TRO is granted, it bridges the gap until the full hearing. If you don’t face a genuine emergency, skip the TRO and go straight to seeking a preliminary injunction.
What You Need to File
The motion lays out your legal arguments and connects them to the four-factor test. The real work is in the supporting evidence. Courts at this stage rely heavily on written submissions rather than live testimony, so your affidavits and declarations carry most of the weight.
- Sworn declarations or affidavits from people with firsthand knowledge of the relevant facts. These need to be specific and factual. A declaration that says “we will lose customers” is weak; one that names specific customers who have said they’ll leave, with dates and communications attached, is strong.
- Documentary exhibits: contracts, emails, photographs, financial records, or anything else that creates a concrete paper trail.
- Expert testimony. When harm or the merits involve technical questions, an expert declaration can explain why the damage is irreparable or why your legal position is sound.
- A memorandum of law explaining how the facts satisfy each of the four factors under the applicable standard.
Affidavits must be notarized.
The Security Bond
Federal Rule of Civil Procedure 65(c) requires the movant to post security before the injunction takes effect. The bond protects the defendant: if the court later determines the injunction was wrongful, the defendant can recover its losses up to the bond amount.3Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders The judge sets the amount based on the potential harm to the defendant, and it can range from nominal sums to hundreds of thousands of dollars depending on the stakes.
You don’t pay the full bond out of pocket. Most litigants purchase a surety bond from an insurance company, paying a premium that’s generally between 1% and 10% of the face value. For a $100,000 bond, that’s $1,000 to $10,000 in premium.
The cap matters in a way that’s easy to overlook. A defendant’s recovery for a wrongful injunction is generally limited to the face value of the bond. If the judge sets it too low relative to the defendant’s actual losses, the defendant may have no way to recover the difference. The bond hearing is worth fighting over from both sides: the movant wants it low to reduce cost, the defendant wants it high as a safety net. The federal government and its agencies are exempt from the bond requirement entirely.3Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders
The Hearing and the Court’s Order
Once the motion is filed and served, the court schedules a hearing. The federal rules don’t prescribe a specific timeline, but courts generally move quickly given the emergency nature of the relief. Where a TRO has been granted without notice, the rules require the preliminary injunction hearing to be set “at the earliest possible time.”3Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders
At the hearing, both sides present arguments. Unlike the TRO stage, the preliminary injunction hearing can include live witness testimony, and parties may subpoena witnesses who aren’t cooperating voluntarily. The defendant gets a full opportunity to present counter-evidence and argue the four factors haven’t been met. The judge may rule from the bench or take the matter under advisement and issue a written opinion days or weeks later.
If the court grants the injunction, the order spells out exactly what conduct is prohibited or required and how long the restrictions last. The injunction stays in force until the court modifies or dissolves it, or the case reaches final judgment. Read the order carefully. Ambiguity in an injunction can become its own source of litigation.
If the Order Is Violated
A party that ignores a preliminary injunction faces contempt of court. Federal courts have the power to punish disobedience of any lawful court order by fine, imprisonment, or both.4Office of the Law Revision Counsel. 18 U.S. Code 401 – Power of Court Civil contempt coerces compliance through escalating daily fines or jail time that ends the moment the party obeys. Criminal contempt punishes past violations with fixed fines or a set sentence.
Even technical or inadvertent violations can trigger sanctions. If you believe the injunction is wrong, seek modification, dissolution, or a stay pending appeal. Don’t just disregard it.
Appealing a Preliminary Injunction
Unlike most pretrial rulings, a preliminary injunction decision can be appealed immediately without waiting for final judgment. Federal law gives appellate courts jurisdiction over interlocutory orders that grant, deny, modify, or dissolve injunctions.5Office of the Law Revision Counsel. 28 U.S. Code 1292 – Interlocutory Decisions This right runs both ways: the defendant can appeal a granted injunction, and the plaintiff can appeal a denial.
Appellate courts review these decisions for abuse of discretion. They won’t second-guess the trial judge unless the ruling rests on a clear legal error, a serious factual mistake, or a decision outside the range of reasonable outcomes. Overturning a preliminary injunction on appeal is hard. If the trial judge applied the right standard and weighed the evidence defensibly, the ruling will stand even if the appellate panel might have come out differently.
Stays Pending Appeal
Filing an appeal does not automatically pause the injunction. Under the federal rules, an injunction remains enforceable while an appeal is pending unless the court specifically orders otherwise.6Legal Information Institute. Federal Rules of Civil Procedure Rule 62 – Stay of Proceedings to Enforce a Judgment To get the injunction suspended while your appeal proceeds, you must first ask the trial court for a stay. If the trial court refuses, you can then ask the appellate court.7Legal Information Institute. Federal Rules of Appellate Procedure Rule 8 – Stay or Injunction Pending Appeal The court may require you to post a bond to protect the other side during the stay.
Modifying or Dissolving an Existing Order
Preliminary injunctions aren’t permanent, and they can be changed when the underlying circumstances shift. The most common basis for modification is new facts: the harm you feared never materialized, the defendant changed its behavior, or a new law altered the legal landscape. Courts have broad discretion to adjust their orders when the original justification no longer holds.
For TROs issued without notice, the rules let the affected party move to dissolve or modify on two days’ notice, and the court must hear and decide that motion promptly.3Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders For preliminary injunctions issued after a full hearing, the path is a motion showing changed circumstances, and the party seeking modification bears the burden. The order remains enforceable until the court says otherwise, and violating it while your motion is pending still counts as contempt.