Constitutional change in the United Kingdom can also be brought about by the use of the royal prerogative, which is the historic source of executive power that is vested in the monarch. This power has evolved over time and is now largely exercised by ministers acting on behalf of the monarch. It includes a range of powers such as the power to make treaties, to declare war, and to grant pardons.

Like conventions, the use of the royal prerogative is not subject to any formal amendment or repeal process, and as such, it presents an alternative path for constitutional change. However, the royal prerogative is subject to legal challenge and has a narrower scope than legislation. In recent years, the use of the royal prerogative has been challenged in court, particularly in relation to the exercise of powers in the context of Brexit.

While the royal prerogative has been used to effect significant constitutional changes in the past, such as the granting of Irish independence, its role in quantitative constitutional change is limited. As such, it cannot be considered as the most important single source of constitutional law in the UK in quantitative terms.

Case Law

Another source of constitutional change in the UK is case law, which involves the interpretation and application of existing laws by the judiciary. The UK has a common law system, which means that precedent plays a significant role in shaping the law. The judiciary has the power to interpret laws and to strike down legislation that is deemed to be unconstitutional.

While case law has been used to effect substantial changes to the constitution, such as the recognition of the right to privacy, its impact on quantitative constitutional change is limited. This is because it is reactive rather than proactive, and its impact is largely limited to specific cases rather than having a broader impact on the constitution as a whole. As such, case law cannot be considered as the most important single source of constitutional law in the UK in quantitative terms.

Statute

Statute, which refers to the laws passed by Parliament, is the most important single source of constitutional law in the UK in quantitative terms. This is because Parliament has the power to make or change laws relating to any aspect of the constitution. Unlike the other sources of constitutional change, the use of statute is subject to a formal legislative process, which provides for debate, amendment and scrutiny.

The doctrine of parliamentary sovereignty means that Parliament has unlimited legislative power, and as such, it is the most effective and efficient means for bringing about constitutional change. Statute can be used to repeal or amend existing laws, to introduce new laws or to create new constitutional structures or institutions.

Furthermore, the role of statute in effecting constitutional change has been reinforced by the role of the courts in interpreting and applying statute. The courts have the power to strike down legislation that is deemed to be incompatible with the constitution, but their role is limited to interpretation rather than legislation. As such, the power to create and change the constitution rests with Parliament, making statute the most important single source of constitutional law in the UK in quantitative terms.

Interpretation and determination of legal legitimacy and the effect of legislation bring case law in line with the constitution. Its reach is wide and has implications for conventions, prerogative, and statutes. However, case law's influence is mainly reactionary, acting as a check and balance to adjust and amend through claimants. Creating a constitutional category of statute imposed a condition on parliament and the function of the constitution. The HRA 1998 provides a distinct constitutional role, with the judiciary scrutinizing the rationale of actions by the executive to balance the rights of individuals and the interests of the community. While having a significant effect on the constitution, case law is better characterized as a custodian than a framer. The effectiveness of case law is limited by political resolve; the government can refine legislation even in the face of legal rebuttal.

The constitutional change effect of legislation is quantifiable, and empirical assessment can be made of its abstract quantitative impact in terms of ongoing influence. The HRA 1998 provides systematic and ongoing influence on the constitution, arguably having a larger quantitative consequence and footprint than other single pieces of legislation.

The example of the Fixed Term Parliaments Act 2011, Miller II, and following legislation illustrates the relative quantitative contributions of the four main sources of constitutional law to amendment. The constitution underwent three substantive changes as a result of legislation interacting with convention, case law, and prerogative.

In conclusion, case law and legislation play significant roles in constitutional change. Case law acts as a gatekeeper to adjust and amend, whereas legislation provides ongoing influence and is quantifiable in its constitutional impact. Examples demonstrate the significant contribution of both sources to constitutional change.

The article presents 40 constitutional conventions and their current status, categorized as accepted and observed, generally observed, often ignored, or challenged. It is sourced from Sharpe, indicating the evolution of constitutional conventions in Westminster democracies. (Source 2)

In the United Kingdom, the constitutional conventions change as the political and legal landscapes shift. The Democratic Audit provides an insightful analysis of when and how this transformation takes place, which is essential for maintaining the UK's democratic system. (Source 3)

Parliamentary approval for military action is a crucial aspect of the UK constitution that is often debated. Claire Mills offers a detailed overview of the process involved and the constitutional conventions that underpin it. (Source 4)

Maddy Thimont Jack, Jess Sargeant, and Jack Pannell propose a framework for reviewing the UK constitution comprehensively. The paper offers a roadmap to assess and strengthen the nation's constitutional setup systematically. (Source 6)