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Should Prerogative Powers be Codified in Statutory Form?

The United Kingdom’s constitution is characterised by the fact that it is not the result of planned design but instead developed organically over time. The ‘Royal’ or ‘Crown’ Prerogative were powers historically vested in the monarch from the era of absolute monarchy. From 1688 onwards, as the country developed towards a democratic constitutional monarchy, prerogative powers have diminished and changed somewhat, but nevertheless remain a residual form of monarchical power.  The government – specifically senior government ministers such as the Prime Minister and the Foreign and Home Secretaries, now wield this power on behalf of the monarch. As a result, the exercise of prerogative power is considered the exercise of executive power without Parliamentary approval. Prerogative power is thus contrasted with statutory power which is created, debated and conferred by Parliament.

Prerogative power continues to play an important role in certain areas such as 'defence of the realm’, diplomatic affairs, Royal Assent, foreign treaties and the appointment of ministers, to name a few. However, prerogative power raises concerns about the extent of the executive’s power as it does not have limitations written into it in the same way that statutory power can, depending on the way in which it is drafted. Prerogative power is therefore a form of pure executive power that could allow the government to act unchecked. Nevertheless, there are legal and political and conventional mechanisms through which prerogative power can be regulated.

The following article will look at two forms of legal means to regulate prerogative power – judicial review and the De Keyser principle, as well as political conventions such as collective ministerial responsibility. Overall, it argues that prerogative power does not need to be codified into statutory form because current mechanisms sufficiently regulate the prerogative and codifying it into statutory form would be ineffective and redundant.

Regulating prerogative power through the De Keyser principle

The development of statutory power has slowly chipped away at prerogative power, serving as a crucial mechanism for regulating the prerogative. As a common law power, the prerogative is subordinate to statute; this is due to the constitutional principle of Parliamentary sovereignty whereby statutory power is seen as a more legitimate form of power as it has undergone the Parliamentary process. Attorney-General v De Keyser’s Hotel Ltd crucially affirmed that statutory power “abridges” prerogative power which can subsequently be considered “in abeyance” or suspended. Therefore, if Parliament regulates a matter, the government cannot use its prerogative power to contradict Parliament’s directives; the prerogative can only be invoked to further the will of the Parliament as expressed in the Act.

A number of subsequent cases have reinforced the De Keyser principle. For example, in R v Secretary of State for the Home Department Ex p. Fire Brigades Union, the Home Secretary attempted to ignore a statutory compensation scheme for criminal injuries approved by Parliament and instead tried to introduce a new tariff scheme using his prerogative power. This was found to be unlawful as it bypassed and frustrated statutory provisions and, hence, ignored the will of Parliament. This is an important limit on the executive’s ability to exercise prerogative power as the development and incursion of more statutory power can dominate areas once governed by the prerogative. Importantly, the Case of Proclamations outlined that prerogative power is a finite source of power so it can be diminished but cannot be added to (BBC v Johns). As a result, new prerogative powers cannot be established – unlike statutory powers, and there must be some precedent in common law to invoke a prerogative power. This serves to limit the extent of prerogative power and allows for statutory power to supersede it. This begs the question of how effective codifying prerogative power into statutory form would actually be since the prerogative is currently already in a subordinate position to statute. It can therefore be argued that the means of regulating the prerogative power through the De Keyser principle is a sufficient mechanism.

Regulating prerogative power through judicial review

Courts can maintain the separation of power and uphold the rule of law by reviewing the government’s use of prerogative power, thereby holding the executive accountable. Prerogative power is only legally enforceable because it is recognised and accepted by courts through common law. As a result, courts have always had the responsibility for identifying the existence of a prerogative power and its extent. However, the Council for the Civil Service Unions v Minister for the Civil Service (GCHQ) developed the scope of judicial review further by establishing that the exercise of prerogative power by the executive is just as amenable to judicial review as their exercise of statutory power. Prior to this, courts had simply reviewed the legality of prerogative power (whether or not the government had the prerogative power they were claiming to and the scope of that power) – they did not conduct a substantive review of how that prerogative power was actually used. The GCHQ case expanded the breadth of judicial review into the executive’s use of prerogative power, allowing the judiciary to ensure the government does not overreach its authority and enjoy arbitrary power.

GCHQ held that prerogative power does not have any special status which exempts it from judicial review and, as a form of executive power, it can be subject to the same scrutiny as statutory power. Courts no longer consider the source of the executive power they are reviewing but rather the nature and way in which it is exercised to assess any “irrationality” or “procedural impropriety”. This was seen in practice in R v SoS for Foreign and Commonwealth Affairs, ex parte Everett where the Foreign and Commonwealth Office’s refusal to grant a new passport for a UK national for whom an arrest warrant had been issued was considered a justiciable matter. Although the FCO argued that the power to grant passports was under the umbrella of prerogative power related to diplomatic relations, the Court of Appeal looked at the “subject matter” of the issue rather than where the powers originated (i.e. whether they were prerogative or statutory). They found that the granting of passports is an administrative decision affecting an individual’s rights and freedom to travel and did not have foreign policy implications. This is a good example of how courts can ensure that prerogative power is not exercised arbitrarily simply because a precedent exists but rather critically evaluates whether that power is appropriately exercised. If prerogative power is reviewed in the same way as statutory power, codifying it into statutory form seems redundant as it would not allow it to be scrutinised any more than it already is. Judicial review is therefore an effective means of regulating the prerogative power of the executive.

Regulation of prerogative power through political or conventional avenues

A significant means of controlling the prerogative is through political conventions. The doctrine of collective ministerial responsibility, for instance, requires the government to have the continued confidence of the Parliament or the Opposition can launch a ‘vote of no confidence’ and exert conventional pressure on the Prime Minister to resign. This holds the government to account for its actions and can allow the legislative to check the prerogative power of the executive. Another such convention which has developed over the years relates to the Prime Minister’s prerogative power to launch military interventions. Although not strictly required, the Prime Minister can propose military action to Parliament, allowing the House of Commons to debate its merits and offer its approval. This is an important check on the Prime Minister’s prerogative power to mobilise the armed forces under the umbrella of ‘defence of the realm’. Arbitrarily involving the armed forces could threaten the government’s position and lead to a vote of no confidence.

While some argue that conventions lack enforcement mechanisms, it is important not to understate their value. These are part of the UK’s significant constitution and therefore have strong political weight attached them as the government can face criticisms for failing to comply. It is also important to note that conventions such as these are flexible as they are amenable to change – an important characteristic for ensuring “effective administration, especially in times of national emergency”. Codifying certain powers related to political crises and conflict, for example, would result in “insufficiently flexible statutory powers which fail to adequately respond to the situations at hand and may result in delays in responses. Waiting for long legal proceedings or enforcing statutory provisions can be extremely disadvantageous when a quick and decisive response is required. Therefore, codifying the prerogative could be overly restrictive, to the detriment of the country. Instead, political and conventional avenues are more appropriate for regulating such sensitive matters.

Limitations of codifying prerogative powers

There are some uses of prerogative power which are considered non-justiciable. This is because they are purely political matters which the judiciary is “ill-qualified” to preside over, as explained in GCHQ. This is an important component of the principle of separation of powers whereby the judiciary cannot overextend itself and must act within its powers. Commenting on the GCHQ case, Lord Roskill outlined some key areas of high policy which were not “amenable to the judicial process” because of their “nature and subject matter”. Generally, matters of ‘high policy’ are seen to be within the remit of the executive rather than the judiciary as they are more political and hence related to the concerns and expertise of the government.

Courts are therefore likely to be more deferential to the executive in cases concerning control of the armed forces, diplomatic relations and treaty negotiations, adopting a lower ‘intensity’ of review. For instance, in R (on the application of Abbasi) v Secretary of State for Foreign and Commonwealth Affairs held that the detention of a UK national in Guantanamo Bay was an area in which English courts had minimal competence and, instead, the government was more appropriately skilled to handle such an issue. The matter was considered justiciable as the detainee’s family had legitimate expectations of support and the Foreign Office had a duty to provide diplomatic assistance. However, courts could not offer a substantive review of the degree and effectiveness of the assistance provided.

Codifying prerogative power into written form will not make them amenable to more strenuous judicial review because they will still be considered non-justiciable issues and the same concerns regarding the effectiveness of the judiciary to adjudicate on such matters would persist. Similarly, prerogative powers such as the creation of peers, granting of honours and appointment of ministers are more political judgement calls. Courts are limited in their adjudication of such matters beyond the pure legality of the decisions taken. As they are not suitable for legal adjudication, it is unclear how codifying them in statutory form would be an effective way of regulating them. It also begs the question whether this would overextend the powers of the judiciary in matters in which they have limited expertise, thereby threatening the separation of powers. In this way, codifying prerogative power into statutory form is an ineffective means of regulating them and, instead, existing legal means of judicial review appear sufficient.

There are examples of prerogative powers being codified into statutory form. For example, the Constitutional Reform and Governance Act 2010 serves as a check on certain prerogative powers exercised by the executive. Firstly, it gives statutory footing to the prerogative of appointing civil servants. By codifying the ways in which the powers should be used (on the basis of “fair and open competition”), it establishes how the government should act and ensures that they cannot deviate from these prescribed codes. The Act also dictates the executive’s prerogative power to enter into international treaties by giving Parliament 21 days to raise any oppositions before they are ratified. However, it is important to note that the Act is limited in that it only addresses certain aspects of prerogative power. Considering the wide breadth and scope of prerogative powers, it would be unfeasible to codify them all into statutory form. There is no exhaustive list of prerogative powers and instead, courts are relied upon to establish whether a prerogative power exists. Logistically, it seems impossible to codify all prerogative powers into statute, notwithstanding the arguments raised above about whether this is even an appropriate way of regulating certain prerogatives. As a result, the existing legal means and political and conventional avenues are sufficient and effective in regulating prerogative power.


In conclusion, this essay has explored two main legal means through which prerogative power can be regulated: through the introduction of statutes as per the De Keyser principle which places prerogative power in a subordinate position to statutory power, and through judicial review. In a post-GCHQ context, prerogative power is just as amenable to substantive review as statutory power which, along with the priority awarded to statutes over the prerogative, is a sufficient means of regulating prerogative power. There are indeed limits to the extent of judicial review in matters of ‘high policy’ which are considered too political for the judiciary to effectively adjudicate on. These matters would also be inappropriate to codify into statute because they will not be any more reviewable as statutes and the same issues of justiciability would persist. Moreover, there are several issues – such as those relating to national emergencies, which serve better as prerogative powers than as statutes due to their urgency. In these cases, other mechanisms of regulation (such as political conventions) are more effective because they allow some flexibility where statutes would not and enable a quick and decisive response. The sheer breadth and scope of prerogative powers makes codifying them into statute a daunting, and perhaps unattainable task, particularly if more effective methods of regulation are available. For these reasons, prerogative power should not be codified into statutory form.


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