A writ of mandamus is a prerogative writ which may be issued by the Supreme Court to command a decision- maker to perform a public duty imposed on him. A fourth means of impugning such decisions involves a review of the legal basis of the decision, including the failure to make a decision, by means of the prerogative writs (in particular, certiorari, prohibition and mandamus and the remedies of injunction and declaration. The impugning of administrative decisions in the Supreme Court by means of these remedies, as distinct from the other means referred to above and an action for damages in tort or for breach of contract,
One ground on which mandamus may be refused warrants special mention, namely, that mandamus will not be granted unless it is necessary. The best way of establishing that mandamus is necessary is for the applicant to show that he has demanded that the duty be performed and that the decision-maker has failed to comply with that demand.
Altho ugh there are grounds for review which are common to two or more of the remedies, there are also differences in the grounds between the remedies which add to the difficulty of choosing the most appropriate remedy and the remedy most likely to be successful. A breach of the rules of natural justice is a ground of review for certiorari, prohibition, injunction and declaration. However, it is not clear whether a breach of the rules of natural justice will amount to a constructive refusal to perform a duty and so provide a ground for seeking mandamus. Fraud is another ground which is common to certiorari, prohibition, injunction and declaration.
The validity of an administrative decision may also be challenged in civil or criminal proceedings. For example, a person charged with an offence created by a regulation may be able to claim that the regulation is invalid because it is inconsistent with the statute under which it was purported to be made.