A preliminary injunction, in equity, is an injunction entered by a court prior to a final determination of the merits of a legal case, in order to restrain a party from going ahead with a course of conduct or compelling a party to continue with a course of conduct until the case has been decided.f the case is decided against the party that has been enjoined, then the injunction will usually be made permanent. If the case is decided in favor of the party that has been enjoined, the injunction will usually be dissolved or dismissed.