1. Written Constitution
A written constitution can be defined as a constitution in which the rules, regulations, principles and practices are found in a single document officially called the constitution. For example the Nigerian Constitution of 1999 and the United States of America Constitution of 1789. It is most commonly adopted in countries with long history of political violence.
2. Unwritten Constitution
This can be defined as a constitution in which the rules and provisions are not found in a single document. This does not in any way mean that such a country does not have a constitution instead it means that there are no comprehensive documents specifying the provisions of such a constitution. In unwritten constitution not everything is written down in black and white. Example of an unwritten constitution is the British Constitution.
3. Unitary Constitution
By the word Unitary, we mean that all power is being concentrated in one level of government. This means that the central government decides all the powers within the State. They may be local governments and regional governments but such government derive their power from the central government. In this case what we have is centralisation of powers rather than the devolution of powers. Thus, Dicey defines it as a single integrated system of government for the exercise of all powers.
4. Federal Constitution
The word Federal is derived from a Latin word FOEDUS which means “treaty” between two or more units. Primarily, the basis of a federal constitution is that it divides constitutional powers between the central and the regional or state units. The powers of each unit are defined by the constitution in such a way that there is coordination and local independence. Nigeria, United States of America, Canada, Switzerland and Australia are examples of countries with Federal Constitution.
5. Confederal Constitution
The Confederal Constitution states the relationship between sovereign states on a common course of action and on certain specified international circumstances. What therefore binds these sovereign states together is not much of what can be described as a constitution but a mere treaty of alliance. The confederal constitution has no direct effect on the sovereign nations. The citizens of sovereign states can only obey the constitution of their countries. The common authority of a confederation deals only with the government of the constituent units. A confederation is a league of membership from which member states have the right to withdraw or secede.
6. Rigid Constitution
These are constitutions which are very difficult to amend or change. The constitution requires a special process of amendment. Nigeria and the United State of America operate rigid constitutions. Several resolutions proposing amendments are introduced but only very few have made headways. In some cases, after an amendment has been proposed, it must be ratified by the component state. Similarly, its amendment procedure would require the approval of two third majority of the members of parliament or three-quarters of the states in the country.
7. Flexible Constitution
This type of constitution is relatively easy to amend or change. The flexibility of the constitution depends on the amendment process. A constitution can be said to be flexible if it can be approved by a vote of a simple majority of the members of parliament. The flexible constitution does not require a two third majority approval or three quarters of the states legislature. Great Britain, Ghana, France and Italy are examples of countries that operate flexible constitution.
We can define Constitutionalism as a means of limiting the powers of government. According to Montesquieu, “it is a means of limiting arbitrary government and tyranny”. We should note that the mere existence of the constitution does not mean the existence of orderly government in the society. There may be tyranny inspite of the existence of the constitution. We can define arbitrary rule as a government which is not operated according to the rules of the constitution but according to the interest of the people in power.