To get a preliminary injunction in California, you file a motion asking the court to order the opposing party to stop (or, less often, to take) some specific action while your lawsuit is pending, and you must show two things: a reasonable probability that you will win the case at trial, and that the harm you would suffer without the injunction outweighs the harm the other side would suffer with it. The court weighs those two factors on a sliding scale, so strong evidence on one can make up for a closer call on the other. Because this is extraordinary relief, expect strict compliance with notice rules, a detailed evidentiary record built on sworn declarations, and a bond requirement before the order takes effect.
What You Must Show
California’s framework comes from the Supreme Court’s decision in IT Corp. v. County of Imperial, and it turns on two connected questions.1Justia Law. IT Corp. v. County of Imperial (1983)
A Reasonable Probability of Winning
You do not have to prove your entire case at this stage, but you have to give the judge enough to make a tentative assessment that your legal claims have real substance. That assessment is built from declarations, documents, and legal argument. Speculation and unsupported allegations will not clear the threshold.
The Balance of Interim Harms
The court then compares the injury you would suffer without the injunction to the injury the opposing party would suffer with it. The sliding scale matters here. If your evidence of likely success is strong, the court can grant relief even when the harm balance is close. If the threatened harm to you is severe and cannot be undone, the court may issue the injunction on a less certain showing on the merits. The goal is to place the greater risk of injustice on the side that can better absorb it while the case moves toward final judgment.1Justia Law. IT Corp. v. County of Imperial (1983)
One practical wrinkle: mandatory injunctions, which order the other party to do something rather than stop doing something, face a higher bar. Courts are more willing to preserve the existing situation than to compel action while the case is pending, so expect closer scrutiny if your motion asks the court to make someone act.
Grounds Recognized by California Law
Your request has to fit within one of the situations the Code of Civil Procedure recognizes as appropriate for injunctive relief. The most commonly invoked are:
- Ongoing or threatened conduct that would cause irreparable injury during the litigation.
- Circumstances where money damages after trial would not make you whole, or where those damages would be extremely difficult to calculate.
- Conduct that would render a future judgment ineffectual by dissipating or transferring the property or interest at issue.
- The need to prevent a multiplicity of lawsuits arising from the same conduct.
- Enforcement of duties arising from a trust relationship.
Irreparable injury is the workhorse ground. Destroyed business relationships, disclosed trade secrets, and demolished property are the archetypal examples: real damage that no later award of money can truly fix.2California Legislative Information. California Code of Civil Procedure Section 526
What to File and How to Serve It
You can start in one of two ways. A noticed motion follows the standard motion rules. An order to show cause (OSC) is issued by the court and is required if you are also seeking a temporary restraining order, or if the opposing party has not yet appeared in the case. When the opposing party has not appeared, the OSC has to be served the same way as a summons and complaint.3Judicial Branch of California. California Rules of Court 3.1150 – Preliminary Injunctions and Bonds
The core papers are:
- A notice of motion or OSC that tells the opposing party what you are asking for and when the hearing will take place.
- A memorandum of points and authorities explaining, with statutes and case law, why the two-factor test favors granting the injunction.
- Declarations from you and any witnesses providing the sworn factual foundation for irreparable harm, the inadequacy of money damages, and your likelihood of prevailing.
- A proposed order spelling out precisely what conduct is being prohibited or required.
If you have previously sought similar relief in the same case, your application must say so and explain what happened. Judges look poorly on parties who quietly try again for a different result.3Judicial Branch of California. California Rules of Court 3.1150 – Preliminary Injunctions and Bonds
California law prohibits granting a preliminary injunction without notice to the opposing party.4California Legislative Information. California Code of Civil Procedure Section 527 On a noticed motion, all moving papers must be served at least 16 court days before the hearing. Mail service within California adds five calendar days; overnight delivery adds two. The opposing party’s opposition is due nine court days before the hearing, and your reply is due five court days before.5California Legislative Information. California Code of Civil Procedure CCP 1005 These deadlines are firm. Missing service gives the other side grounds to continue or defeat the hearing, and delay in this kind of case can be fatal.
When You Need Emergency Relief First
If the harm is so imminent that even 16 court days is too long, you can ask for a temporary restraining order to hold things in place until the preliminary injunction hearing. You or your attorney have to appear in person before the judge to request one.3Judicial Branch of California. California Rules of Court 3.1150 – Preliminary Injunctions and Bonds
A TRO can issue without advance notice to the other side only if two conditions are met. Your sworn evidence must show that serious or irreparable injury will occur before the matter can be heard on normal notice. And you or your attorney must certify under oath that you either notified the opposing party of the application, tried in good faith but could not reach them, or have specific reasons that justify not giving notice.4California Legislative Information. California Code of Civil Procedure Section 527
Once a TRO is granted, the preliminary injunction hearing must be scheduled no later than 15 days later, or 22 days if the court finds good cause. Within five days of issuance, or two days before the hearing, whichever comes first, you must serve the opposing party with the complaint, the OSC, your supporting declarations, and your legal brief. Miss those service requirements or fail to be ready at the hearing, and the court will dissolve the TRO.4California Legislative Information. California Code of Civil Procedure Section 527
The Bond You Must Post
When the court grants your preliminary injunction, it must also require you to post an undertaking before the order takes effect. The bond protects the opposing party: if the court later decides you were not entitled to the injunction, the bond covers the damages that party suffered because it was in place.6California Legislative Information. California Code of Civil Procedure Section 529
The court sets the amount by estimating the potential financial harm the injunction may cause the restrained party, which can include lost revenue, disrupted operations, and attorney’s fees. You typically obtain the bond through a surety company.
You must present the undertaking within one court day after the injunction is granted, unless the court sets a different deadline.3Judicial Branch of California. California Rules of Court 3.1150 – Preliminary Injunctions and Bonds The restrained party has five days after being served with the injunction to object that the bond is insufficient. If the court agrees and you cannot post an adequate bond within the time allowed, the injunction dissolves.6California Legislative Information. California Code of Civil Procedure Section 529
Cases involving challenges to housing development projects are treated differently. A separate statute caps bond liability at $500,000, permits the court to consider evidence of the plaintiff’s economic hardship when setting the amount, and gives the court discretion to waive the bond entirely if any bond would cause undue economic hardship.7California Legislative Information. California Code of Civil Procedure Section 529.2
The Hearing and the Written Order
Both sides argue at the hearing, but the judge’s decision rests on the written submissions. Your declarations, exhibits, and briefs carry the weight; oral argument is your chance to highlight the strongest parts of that record and answer the judge’s questions. You cannot introduce new evidence orally, so the papers must stand on their own.
If the court grants relief, the written order must describe the specific acts being prohibited or required. Vague orders create enforcement problems and are vulnerable on appeal. A well-drafted order also lays out the court’s reasoning on both prongs of the test: its assessment of your likelihood of success and its weighing of the comparative harms.
After the Order: Compliance, Changes, and Appeal
Disobeying a preliminary injunction is contempt of court.8California Legislative Information. California Code CCP 1209 – Acts or Omissions Constituting Contempt A person found in contempt faces a fine of up to $1,000, imprisonment for up to five days, or both, and the court can order the violator to pay the reasonable attorney’s fees and costs incurred by the party who brought the contempt proceeding.9California Legislative Information. California Code of Civil Procedure CCP 1218 A party who believes the order was wrongly issued has legal avenues to challenge it, but ignoring it is not one of them.
The injunction is not permanent. Either party can ask the court to modify or dissolve it on notice by showing a material change in the underlying facts, a change in the applicable law, or that the ends of justice require modification.10California Legislative Information. California Code CCP 533 – Modification or Dissolution of Injunction “Material” is the operative word. Rehashing arguments the court already rejected will not work, and evidence that was available at the original hearing but was not presented generally does not qualify either.
Unlike most pretrial rulings, an order granting or denying a preliminary injunction is immediately appealable.11California Legislative Information. California Code CCP 904.1 – Appealable Judgments and Orders Either side can appeal without waiting for final judgment. Filing an appeal does not automatically stay the injunction, so a party who has been enjoined and wants relief during the appeal typically has to seek a separate stay from the trial court or the appellate court.