Interlocutory Injunction in UK Law

American Cyanamid v. Ethicon which enjoins the judge upon an application for an interlocutory injunction to direct his attention to the balance of convenience as soon as he has satisfied himself that there is a serious question to be tried, was not dealing with a case in which the grant or refusal of an injunction at that stage would, in effect, dispose of the action finally in favour of whichever party was successful in the application, because there would be nothing left on which it was in the unsuccessful party's interest to proceed to trial.

Where, however, the grant or refusal of the interlocutory injunction will have the practical effect of putting an end to the action because the harm that will have been already caused to the losing party by its grant or its refusal is complete and of a kind for which money cannot constitute any worthwhile recompense, the degree of likelihood that the plaintiff would have succeeded in establishing his right to an injunction if the action had gone to trial, is a factor to be brought into the balance by the judge in weighing the risks that injustice may result from his deciding the application one way rather than the other.

A right to obtain an interlocutory injunction is not a cause of action. It is dependent upon there being a pre-existing cause of action against the defendant arising out of an invasion, actual or theatened by him, of a legal or equitable right of the plaintiff for the enforcement of which the defendant is amenable to the jurisdiction of the court. The right to obtain an interlocutory injunction is merely ancillary and incidental to the pre-existing cause of action.

However it must be remembered that the grant of an interlocutory injunction is a discretionary remedy that should be available to prevent injustice. But if the claimant has a cause of action to protect a property right recognised by the law, there is no reason in principle why the court should not grant an interlocutory injunction to protect that right, even if damages are not recoverable.

Situation (1) is when one party to an action can show that the other party has either invaded, or threatens to invade, a legal or equitable right of the former for the enforcement of which the latter is amenable to the jurisdiction of the court. Situation (2) is where one party to an action has behaved, or threatens to behave, in a manner which is unconscionable.

It may set aside the judge's exercise of his discretion on the ground that it was based upon a misunderstanding of the law or of the evidence before him or upon an inference that particular facts existed or did not exist, which, although it was one that might legitimately have been drawn upon the evidence that was before the judge, can be demonstrated to be wrong by further evidence that has become available by the time of the appeal: or upon the ground that there has been a change of circumstances after the judge made his order that would have justified his acceding to an application to vary it.

An interlocutory injunction, like any other injunction, must be expressed in terms which are clear and certain. The injunction must define precisely what acts are prohibited. The court must ensure that the language of its order makes plain what is permitted and what is prohibited. A person should not be put at risk of being in contempt of court by an ambiguous prohibition, or a prohibition the scope of which is obviously open to dispute.