The concept of a constitution is discussed by KC Wheare in Modern Constitutions (1966),
.. the word 'constitution' is commonly used in at least two senses in any ordinary discussion of political affairs. First of all it is used to describe the whole system of government of a country, the collection of rules which establish and regulate or govern the government.. In almost every country in the world except Britain however, the word 'constitution' is used.. to describe not the whole collection of rules, legal and non-legal, but rather a selection of them which has usually been embodied in one document or in a few closely related documents....
Types of Constitution
Wheare distinguishes constitutions through consideration of a number of aspects.
Written and Unwritten
Most constitutions are enacted or codified, either in a single document or series of documents. Many countries have followed the models of the US or French constitutions.
The UK constitution is considered to be unwritten, despite key documents such as the Human Rights Act 1998 which could be viewed as constitutional documents there is no systematic code. The only other states not to have entirely written constitutions are New Zealand and Israel.
Rigid and Flexible
The ease with which a constitution can be altered is a factor. Some are classed as rigid if they require a special process before they can be changed. This process is usually more onerous and so restricts the ability to change a constitution compared to other laws. To amend the Bill of Rights in the US Constitution requires a two thirds majority of both Houses of Congress and ratification by three quarters of State legislatures. In the Republic of Ireland amendments must be passed by the legislature and then approved by a majority in a referendum.
The UK constitution is described as flexible as it requires only the normal procedure to pass on Act of Parliament, essentially a majority in both the Houses, to change any written law elements. The UK constitution also includes non legal rules which can be changed without any formal procedure.
Supreme and Subordinate
A supreme constitution is not subject to any external superior force. A subordinate constitution is drafted and introduced in a country by an external sovereign power, so could be amended by that external power. At the core of the distinction is whether the constitution provides the highest form of law in the land. For example subordinate constitutions can be found in federal systems and in countries which have gained partial independence but are a limited government.
The UK constitution is viewed as supreme. Although, the constitutional impact of UK membership of the European Union (EU) is debated. It can be argued that UK sovereignty is limited by EU treaties but it can be seen this limitation is voluntary, under an Act of Parliament - European Communities Act 1972 and therefore does not alter supremacy.
Federal and Unitary
The internal division of power within a state is an important aspect. In a unitary state only the central government has primary law making powers, powers may be delegated to lower tiers only. In a federal state, both the central government and the individual territories comprising the federation have primary powers. For example, in US the individual States have autonomy to legislate on some matters.
Despite devolution, the UK remains a unitary state, with Parliament having the ultimate law making power over all the constituent nations.
Republican and Monarchical
In republics, there is no monarchy and there will normally be a President, who is a directly elected Head of State, such as in the US. In some republics the President can be restricted to a more formal role of a figurehead, such as Italy or Germany.
The UK remains monarchical, with the Queen as Head of State. The monarch continues to hold formal powers under the royal prerogative, although in practice these are exercised by the elected Government.
A constitution's legitimacy is an important element. Thomas Paine observed that
.. a government without a constitution is a government without right... (Rights of Man (1791)).
Beetham argued that
.. three conditions are required: its conformity to established rules; the justifiability of the rules by reference to shared beliefs; the express consent of the subordinate, or of the most significant among them, to the particular relations of power... (The Legitimation of Power (1991)).
Legal Exercise of Powers
Constitutions allocate and limit powers. A written constitution provides a higher law in itself. It may provide courts the power to strike down legislation, which can make laws both illegal and unconstitutional . The US Supreme Court has decided it has the power to carry out such reviews even though there is no such provision in the constitution (Marbury v Madison (1803)).
In the UK, Parliamentary Supremacy and common law rules govern the exercise of power. The doctrine of Parliamentary Supremacy limits the ability to challenge legislation in the courts, therefore it may be possible for laws to be unconstitutional but not illegal.
Many written constitutions result from a revolution or key historical event so inherently try to embody a set of representative ideals. Constitutions often contain a set of fundamental rights, explicitly the Bill of Rights in the US constitution. A written constitution will often name the people as the ultimate source of authority.
In the UK the Human Rights Act 1998 sets out number of individual freedoms.
Constitutions are often approved by democratic means which lays a foundation for continued acceptance.