The usual test for an interlocutory injunction comes from the Supreme Court of Canada’s decision in RJR—MacDonald Inc. v. Canada (Attorney General). For a conventional interlocutory injunction that restrains conduct, the moving party generally must establish three things: a serious question to be tried, irreparable harm if the injunction is refused, and that the balance of convenience favours granting the order.
An interlocutory injunction is an exceptional remedy sought before the underlying dispute has been finally determined. The court is therefore being asked to intervene while the parties’ substantive rights remain unresolved. The evidence and the practical consequences of granting or refusing the order are central to the analysis.
1. Is there a serious question to be tried?
The first stage asks whether there is a genuine legal or factual issue requiring determination. Under the conventional RJR—MacDonald test, this is generally a relatively low threshold: the court does not normally conduct a full trial of the merits at the interlocutory stage.
The claim must nevertheless have sufficient legal and evidentiary substance to justify proceeding to the remaining stages of the injunction analysis.
Because “serious question to be tried” has its own legal meaning and important qualifications, see What does “serious question to be tried” mean in an Ontario injunction motion?.
2. Would refusing the injunction cause irreparable harm?
The moving party must next demonstrate that refusing interlocutory relief would expose it to harm that could not adequately be remedied later.
“Irreparable” refers principally to the nature of the harm, not simply its financial size. The issue is whether damages or another remedy available after trial would adequately address what occurred while the case was pending.
This requirement is often critical in urgent commercial disputes involving confidential information, restrictive covenants, business relationships, property, or other circumstances in which waiting until final judgment may materially change the parties’ positions.
See What does “irreparable harm” mean in an Ontario injunction motion? for the second branch of the test.
3. Where does the balance of convenience lie?
The third stage requires the court to compare the practical consequences of granting the injunction with the consequences of refusing it.
The court considers which party is likely to suffer greater harm from the interim decision pending final determination of the dispute. This assessment is contextual and can include the interests of the parties, preservation of the existing position, the effect of the proposed order, and other circumstances relevant to whether interlocutory relief is equitable.
The three parts of the test operate together. Establishing that there is a serious dispute does not, by itself, establish entitlement to an injunction.
See What does “balance of convenience” mean in an Ontario injunction motion? for the third branch of the analysis.
Does the same test apply to a mandatory injunction?
Not exactly.
Where the requested interlocutory order is mandatory in substance—meaning that it requires the responding party to take positive action—the first stage is more demanding.
In R. v. Canadian Broadcasting Corp., 2018 SCC 5, the Supreme Court of Canada held that the moving party generally must establish a strong prima facie case, rather than merely a serious question to be tried. The applicant must still demonstrate irreparable harm and that the balance of convenience favours granting the order.
This is why the practical effect of the requested relief matters. An order requiring a party to restore, deliver, remove, return, or otherwise take a positive step can engage the heightened mandatory-injunction standard.
See What is a mandatory injunction in Ontario? for that distinction.
What evidence is required on an injunction motion?
An injunction motion must be supported by evidence addressing the elements of the applicable test.
Depending on the case, that may include affidavit evidence, contracts, correspondence, financial information, corporate records, evidence concerning confidential information, and documents showing the urgency and expected consequences of granting or refusing relief.
The motion proceeds within Ontario’s Rules of Civil Procedure, while section 101 of the Courts of Justice Act gives the Superior Court of Justice authority to grant an interlocutory injunction or mandatory order where it appears just or convenient to do so.
How does ME Law assess an interlocutory injunction?
ME Law assesses the underlying legal claim, available evidence, urgency, anticipated harm, balance of convenience, and practical scope of the proposed order before determining whether interlocutory relief should be pursued or opposed.
The analysis also considers whether the requested order merely restrains particular conduct or is mandatory in substance, because that distinction can change the first-stage merits threshold and the evidentiary record required.
Contact ME Law if you are considering an interlocutory injunction or need to respond to an urgent injunction motion.