In the past the courts have viewed the exercise of certain types of prerogative powers as being essentially political rather than legal matters and the courts tend to treat such matters as being non-justiciable. These include such powers as the dissolution of parliament, executive assent to legislation and making of treaties with foreign states.
In PF ZAPU v Minister of Justice (2)1985 (1) ZLR 305 (S) at 315-316 the Supreme Court started off by stating that these powers were not normally subject to judicial review. However, it went on to say that the court would check to see that these powers were exercised under lawful conditions and within the law. It said that a court of law could thus review and set aside the exercise of a prerogative power of the President if its exercise had resulted in a person being deprived of his/her rights, interests or legitimate expectations without being heard from first. For example, if the President exercised the prerogative of mercy without first obtaining the advice of the Cabinet as required by the Constitution, the court would be entitled to declare the President’s action unlawful.
See also Linington The Constitutional Law of Zimbabwe pp 84-94.
There has been an increasing trend in a number of countries to subject prerogative to some extent of review. In South Africa there have been a number of cases in which this issue has arisen. In Re Certification of the Constitution of the Republic of South Africa 1996 (10) BCLR 1253 (CC) the Constitutional Court decided that the exercise of a prerogative power could be reviewable if the power was exercised in a way which undermined provisions of the Constitution.
In the case of President of the Republic of South Africa v Hugo 1997 (6) BCLR 708 (CC), the court held that the exercise of the President’s power to pardon or reprieve offenders as set out in the constitution was subject to judicial review. The President had granted a remission of the remainder of their sentences to certain categories of prisoners. One of these was to all mothers with minor children under the age of 12. The respondent, who was a widower with a young son, had argued that this remission was discriminatory and therefore contrary to the Constitution. The Constitutional Court held that although the measure had discriminated against the respondent, the discrimination was not unfair in the circumstances. However, Court also decided that the President’s power was subject to judicial review because it was a power conferred by the Constitution. It was subject to review in the same way as other constitutional powers were subject to review. If the discrimination has been unfair the Court would have been entitled to order that remedial measures be taken so as to comply with the Constitution. (In the lower court Goldstone J referred to the view of Baxter that prerogative powers were an historical anachronism and that such powers should be subjected to review.
In England as well the courts have shown an increasing willingness to review the exercise of prerogative powers. In CCSU v Minister of the Civil Service  3 All ER 935 (HL) the majority of the court accepted that prerogative powers are justiciable in the courts. The Minister was exercising a prerogative power when banning trade unions at a government intelligence communication installation. The court required the Minister to adduce evidence that this ban was based on considerations of national security.
In R v Secretary of State for the Home Office, ex p Bentley  4 All ER 442, the prerogative of mercy was subjected to judicial review and the court stipulated the types of considerations that could be taken into account when exercising this power.