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Updated: May 8, 2023

All organisations – whether a sports club or a state – have a set of rules which serve as a constitution. Every society requires fundamental rules in order to function and to ensure order. However, before considering the importance for a state to have a constitution, it is crucial to define what a state is. Even though defining the notion of statehood, in its modern sense, is one of the most controversial issues of international relations, there is a definition, almost universally shared by the international community, coming from international law.

The Montevideo Convention on Rights and Duties of States 1933, art 1 defines a state as follows:

“The State as a person of international law should possess the following qualifications:

(a) a permanent population;

(b) a defined territory;

(c) government; and

(d) capacity to enter into relations with other states”.

In international law, the concept of state recognition has been presented for a long as being a precondition of statehood. However, this issue seems to have been recently solved by modern international law which excludes this factor from the constitutive elements of statehood, as stated in the Montevideo convention. The idea of constitution comes from the historical evolution from the modern State and the Rule of Law: even the government is subjected to certain rules determining what he can or cannot do. These rules are meant to ensure the continuity of the state and its order.


In an attempt to define a constitution, Bradley and Ewing have noted that in a narrow sense, a constitution can be described as: “(…) a document having a special legal status which sets out the framework and principal functions of the organs of government within the state and declares the principles or rules by which those organs must operate”.

But there are other perspectives on what a constitution is about. A social scientific perspective would tend to view the state as those elements in society which, taken together, represent the central source of political, military and economic power; and the constitution of a state is the formal expression at any given time of the allocation of this power as between individuals and groups.

As a conclusion and for the purposes of this chapter, we may conclude that a constitution is a set of supreme rules and principles regulating the organisation and structure of a state, which the governing institution should adhere to. Generally, these rules will be gathered in a written document entitled “Constitution” as being more or less supreme for each state. However, for some states, for instance the United Kingdom, these rules are located other than in a specific constitutional document.

The contents of a constitution

The exact contents of constitutions will vary from state to state. However, there are always common features present in almost every constitution. For example, as an introduction, a preamble will be found in many states constitutions. These preambles are usually symbolic and set the main values ideology of the rest of the text. For instance, the preamble to the United Nations Charter, which serves as a constitution for the organisation although it is not a constitution in the nationalist sense, is illustrative of the ideology and the spirit of the text: “We, the peoples of the united nations”. In this respect, preambles of constitutions tend to be declaratory in nature but they generally identify the people as the constituent or the sovereign power from which the moral authority of the constitution derives.

A constitution will primarily establish the different institutions of the state and set out their different roles, powers and functions. Traditionally, the constitution will establish the legislative, the executive and the judiciary that are the three main powers of the state, divided by function. The law-making institution passes legislation. From state to state, the legislative will be called Parliament, Congress or Assembly. The government is the main institution responsible for complying with the obligations of the state towards its population and making policy decisions. The executive power is generally headed by the Prime Minister but it can also be headed by the President or a cabinet of ministers.

The judicial institution dictates and interprets the law. The courts are usually part of a judicial system which is hierarchal and headed by the Supreme Court or a Constitutional Court. In some judicial systems, such as France, civil and administrative courts are separated and placed under a different hierarchy according to their functions.

The constitution may also confer specific powers to certain institutions. For example, the constitution may provide, by a specific provision of its text, that the President has the power to sign Treaties on the behalf of the state. A constitution will also determine the constitutional relationship between the different institutions that it establishes. For instance, the constitution will generally set out that the Parliament approves by a consulting vote the budget of the executive. This principle, which is inherent to any democracy, refers to the check and balances as it is generally called under US constitutional law. For example in the UK, the constitution establishes the relationship between the Queen and the Parliament in the context of the passage of legislation. Even though the Parliament adopts legislation the Queen is still required to grant Royal Assent to legislation.

Accordingly, a major theme of constitutional law and the study of the level of democracy in a state is how the state institutions work together, and most importantly, how these institutions check and balance one another. As stated above, a constitution will also deal with how the individual relates to the state. Democratic constitutions will do so by conferring fundamental rights to the individual. The enshrinement of these rights in the constitution will impose obligations on the state such as the protection of the life of an individual from murder for example. In this respect, the constitution will accord a special protection for individual’s rights from infringement by the state. However, this list of rights will also contain the justifications to restrictions on individuals’ rights.

Therefore a constitution will also set what powers the state can exert over the individual by regulating for instance in what circumstances an individual can be arrested or detained. To some extent, this can be seen as being a condition part of the social contract signed between the individual and its state. In a democracy, having such a bill of rights in the constitution will legitimate the public powers of the state institutions. One of the most famous declarations of fundamental rights is the French Declaration of Human and Citizens’ Rights (1789), which has been interpreted by the French Constitutional Court as being part of the constitutional bloc.

Finally the constitution will generally contain the methods and procedures to be amended. Given that law is an evolutionary science, constitution have to be capable of being adapted and improved especially when they have been in force for decades or centuries. For example, amendments to the constitution of the United States can be made provided that two-thirds of both the Congress and three-quarters of the state legislatures approve such changes. The French fifth constitution (1958), in its article 89 adds a supplementary condition of popular consultation. This is because the people are considered as being the constituent, having the power to adopt and reform the constitution. As opposed to the theory of national sovereignty, this approach is generally referred to as popular sovereignty.

The purposes of a constitution

The rationale of having a constitution can be explained by several reasons. First of all, as any other organisation, a society needs rules to ensure stability. History, and particularly the middle age, has shown that the lack of regulations resulted on the instability of permanent military conflicts. In this regard, constitutionalism has been a factor of progress for modern societies.

In this respect, a constitution ensures that the state achieves its primary purpose and objectives. For instance, the third and fourth French constitutions have resulted on institutional blockages that prevented the executive from governing the country and the legislative power from adopting laws. This lack of stability inspired the fifth constitution (1958) that reaffirmed the legitimacy and stability of state institutions and particularly the executive.

A constitution also legitimates the state in its actions to maintain public order. The constitution will contain provisions about which institution is able to declare war in case of external attack but also which measures the state can take to efficiently tackle a civil war.

Another function of a constitution will also be to ensure that institutions have certain legitimacy and act with consent of the people. Thomas Paine famously stated: “A constitution is not the act of a government, but of a people constituting a government, and a government without a constitution is a power without right”.

In our modern democracies the legitimacy of a constitution will be enacted through popular consultation. As noted above, according to the popular sovereignty theory, the sovereign is the people. For example, Article 6 section 1 of the Irish constitution specifically underlines this idea: “All powers of government, legislative, executive, and judicial, derive, under God, from the people, whose right is to designate the rulers of the state”. Therefore, once the sovereign, the people, has been granting official assent, the state institutions enjoy the public prerogatives required to govern the people. A safeguard to engage the responsibility of the state when exercising such powerful prerogatives is to enshrine, in the constitution, a bill of rights preventing the exercise of such powers to interfere with individuals’ rights.

A constitution may also serve draw a clear line under an authoritarian past enshrining the values and principles of a new democracy. Needless to quote the numerous historical examples, a constitution may often be adopted after a revolution a drastic change of regime. The role a constitution is not only to distribute public powers amongst the state institutions but also to draw the limits of these powers and the mechanisms to check that they are not misused or abused at the expenses of the individuals.

Finally, a constitution is also a text that gathers the core values of a society and binds its individuals between them. These values keep the individuals of a society united and enable them to progress together towards common objectives. They will vary from state to state and can be for example the public good, the welfare of the population, the promotion of democratic values or the protection of human rights. For instance, the Brazilian constitution, under its Article 3, provides that one of the objective of the state is to eradicate poverty.

Religious states usually confer a special attachment to a religion. Generally, where a specific religion is predominant, this predominance will be enshrined in the constitution. For example, this is the case of the catholic states conferring a particular role to the Church. However, a constitution can also be used to unify different groups or religions or to recognize the rights of certain minorities. For example, the Moroccan Constitution (2011) in its preamble recognizes the Muslim and Jewish cultural identity of its citizens.

The classification of constitutions

Written and unwritten constitutions

A written constitution is traditionally seen as one formulated of one or several written documents. The USA provides a classic example of such a purely formal constitution. Similarly, the Indian constitution is made of one written document that contains 400 articles.

However, other constitutions, such as the French constitution, are comprised of multiple written documents (Déclaration of the Rights of Man and of the Citizen of 1789, Preamble of the 1946 constitution, the 1958 constitution, etc.). For some commentators, such as FF Ridley: “There is no British Constitution”. In this view, a single entrenched written document is the defining characteristic of constitutional states. The UK, in contrast, does not have a “traditional” written constitution. Its constitution has evolved over many centuries, and as a result cannot be found in any single, or even a small group of documents. For traditional constitutionalists, such as de Tocqueville, writing in the first half of the 19th century, the UK's lack of a written constitution left him to remark that in England: “there is no constitution”. However, in line with definitions cited earlier, the UK can certainly be seen as a constitutional state. In addition to this, most of the constitutionalists agree to admit today that the UK has a constitution, although it is not a traditional written constitution. The UK constitution has a body of rules, both written and unwritten, which allocate the functions of the state. This is one of the primary functions of a constitution. Sir Ivor Jennings put it: “If a constitution means a written document, then obviously Great Britain has no constitution ... But the document itself merely sets out the rules determining the creation and operation of governmental institutions, and obviously Great Britain has such institutions and such rules. The phrase ‘British constitution’ is used to describe those rules.” Therefore, it can be said that the UK has a de facto constitution.

Theorists use the distinction between those constitutions that are codified in one or several documents (as in the USA), and those that are uncodified and found from a number of legal sources (as in the UK).Nevertheless, the distinction between written and unwritten is not absolute since it has recently been admitted that other unwritten sources feed a constitution, even in states that have a written constitution. For example, jurisprudence of the national supreme courts interprets the constitution and sets principles that are constitutional. Moreover, written provisions are necessarily supplemented by political practices and conventions that have been developed throughout the state’s constitutional history.

Rigid and flexible constitutions

Historically, a distinction has also arisen based on the process of amending constitutions. Accordingly, a rigid constitution is one where constitutional law can only be amended through a special constitutional procedure. These constitutions require several constitutional obstacles to be overcome as safeguards of the continuity of the state. This is because according to the traditional hierarchy of norms, constitutional law has a higher status than all other forms of national law.

Generally, rigid constitutions are contained in one written document. However, there are exceptions to this trend and the constitution of Singapore provides an example: it is written but flexible. The US Constitution is a very good example of a rigid constitution. In order to make a constitutional amendment; a proposal firstly has to be adopted by both houses in Congress (the legislature) with a two-thirds majority. The proposal then has to be ratified by three-quarters of the states.

On the other hand, a “flexible” constitution is one where constitutional laws can be amended by regular legislative laws. For instance, in the UK, Parliament is the supreme law-making body and it can pass, amend, or repeal any law with a simple majority.

The Human Rights Act 1998, which is recognized as having constitutional value, for example, could be amended or even repealed entirely in exactly the same way as any other Act of Parliament. Accordingly, no special mechanisms are necessary to change important constitutional laws in the UK. The traditional legislative law-making process in the UK implies the consent of both the House of Commons and the House of Lords together with the Royal Assent. This can be explained by the central place of parliamentary supremacy (or sovereignty) in the UK. However, having a flexible constitution does not mean that Parliament, or other bodies entitled to do so, can amend the constitution without any limits. Because of the major importance of the constitution in every state, there are some legal and political constraints on what Parliament can and cannot do.

Unitary and federal constitutions

These classifications have to do with the structure of the state and the devolution of powers or sovereignty from the central to the local level. A unitary constitution has the majority of its legal and executive power vested in the central organs of the state. In the UK, most power is centrally controlled in Westminster and Whitehall. However, some power is devolved to regional bodies, for example local authorities (“councils”), to the London Assembly and most notably (since 1998) through the devolved Parliament in Scotland and the Assemblies in Northern Ireland and Wales.

The devolved nations of the UK have significant but limited jurisdiction in certain areas: their power is given by an Act of the Westminster Parliament (for example, the Scotland Act 1998 and the Government of Wales Act 1998), and the power to repeal those Acts remains with the Westminster Parliament. Therefore, these institutions remain subordinate, in the legal sense, to the supremacy of Westminster Parliament. This phenomenon is referred to by specialists as the decentralization of the power in unitary states and is also illustrated for example, in Spanish or French constitutional history.

In short, even if a unitary constitution recognizes and delegate power to decentralized institutions, they do not have express constitutional protection and do not formally exist as separate entities from the central state, unlike the state/provincial/ legislatures in a federal constitution.

Conversely, in a federal constitution, power is divided between federal government and states or regional authorities. This model is generally established in a constitutional document, for example the German and US Constitutions. These constitutions establish the legal recognition of local states as separated entities, remaining inter-connected by the federation.

Some powers, like state security and foreign policy, are likely to be reserved to central government, but the regional authorities (such as the states in the USA or the German “Bundesländer”) have considerable powers to legislate on and administer their own affairs. For this reason, where the competence to legislate in a specific area belongs to regional states, you will find, within the same federation, different legislations from one state to another. For instance, in the US, since the power to adopt legislation on death penalty remains a state prerogative, some of them have prohibited death penalty and others are still practicing it.

Separated and fused powers

According to the theory of the separation of powers, one of the principles of constitutionalism is that power should be divided and dispersed in order to prevent abuse of power by those in control. This approach fosters checks and balances between the different bodies of the state.

The US Constitution is a clear example of a separated constitution; power is clearly dispersed between Congress, the Judiciary (Supreme Court), and the President. Each body has its own functions though it exercises some control or check over the other two. At the other end of the extreme would be an autocratic or totalitarian regime where power is vested in one body or one individual: this type of constitution is said to be fused. Thus, a separated constitution is an indicator of the democratic nature of a state.

Monarchical and Republican constitutions

A monarchical constitution provides that the head of state is a monarch. Most of the modern states in this category have adopted “constitutional monarchies'’ in which the monarch plays a largely symbolic role with only very limited powers, for example the UK, Spain, the Netherlands and Sweden.

In the UK, Queen Elizabeth II is still nowadays the head of state and all government acts are passed in the name of the Crown. She has a large amount of theoretical legal power but little practical power given that constitutional practices have led to political limits of her powers. Indeed, the Executive, on the Crown's behalf, exercises a large amount of the legal “prerogative” power of the Crown.

On the other hand, a republican constitution is one in which the head of state is usually democratically elected, and is most often known as a President. The degree of power that such leaders have depends on the constitution itself.

In some countries, the President will have very significant political power, as for instance in France and the USA. In other states, though, the President’s role will be largely symbolic and ceremonial, such as in Germany or in the Republic of Ireland. In those countries, the Prime Minister or the Chancellor will be, de facto, the head of the executive.

The basic principles of constitutionalism

The main objective of constitutionalism is to ensure that governments act constitutionally. In other words, each institution of the state has to act in accordance with the rules and principles enshrined in the constitution. This is related to the Rule of Law which is of a crucial importance in the modern state where governance is bound by a legal system allocating and limiting powers.

As stated above, the function of a constitution is not only to describe the powers of governing institutions but also to set out control mechanisms and checks in the constitution. The rationale behind constitutionalism is linked to the separation of powers; the objective is to prevent abuse of power by state institution. To some extent, constitutionalism is a safeguard against the excesses of totalitarianism and authoritarianism. For instance, the executive cannot decide to monopolise legislative and judiciary functions by force just because it finds it necessary.

According to the modern notion of constitutionalism, acting constitutionally also entails to respect for the basic human rights of individuals. In this sense, the fact that the executive of the state is bound by the obligation to act constitutionally, prevents him, at least legally, to commit violations of individuals’ rights. For instance, in the UK constitution, constitutionalism implies that the use of public power is controlled in accordance with the following principles:

  • Basic rights of the individual are enshrined and safeguarded;

  • Public power is separated amongst the different state institutions;

  • When exercising public power, state institutions should act strictly within their legal prerogatives and limits;

  • An independent and impartial court system should review the constitutional use of public power; and

  • The Kingdom should adhere to the basic principles and values of democracy.



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