Doctrine of separation of powers was first propounded by the Frenchman called Baron de Montesquieu, in his book ‘the spirit of the laws’ written in 1748. He strongly believed that the civil liberty which the 18th century England enjoyed was derived from the separation of powers among the three organs of government.
In order to avoid tyranny and oppression, those who make laws should be different from those who interpret the law and punish the offenders. The Executive also should be different from the judiciary and the Executive and Judiciary should be separated from the legislature.
The members of the Executive should neither be members of the legislature nor the member of the judiciary. One organ of government should not control or influence the functions of the others. If there is no separation of powers of government, there might be tyranny, oppression and victimization.
It is a practice among most democratic countries to put this doctrine of separation of power in their constitution in order to protect individual liberty and freedom.
Taking Nigeria, Ghana and Gambia as our example, the executive which govern in any of these countries are different from the law making body (the legislature) and the legislature is different from the judiciary. In presidential system of government, individual ministers or adviser is responsible only to the president who appoints him.
HOW SEPARATION OF POWER WORKS IN PRESIDENTIAL SYSTEM OF GOVERNMENT
In presidential system of government there is a clear separation of powers. The president and his body of advisers or ministers are different from the parliament.
In the same vein, the judiciary is also separate from both executive and the legislature.
This shows that there is a clear separation of powers among the three organs of government.
Nigeria and United States of America offer good examples of the countries that practice presidential system of government.
This is because in Nigeria, the president and his Ministers have the executive powers and are not members of the legislature.
Again in United States of America, the president and his ministers are not members of the congress.
HOW SEPARATION OF POWERS WORKS IN CABINET SYSTEM OF GOVERNMENT
In cabinet system of government there is a union of power between the executive and the parliament.
The cabinet system has a parliamentary executive which is accountable to the parliament.
In reality, there is no complete separation of powers between the executive and the parliament; the executive can always get support from the parliament since the members of the executive are also members of the parliament.
THE PRINCIPLE OF CHECKS AND BALANCES
The principle of checks and balances is a complement to the doctrine of separation of powers.
This principle of checks and balances means that power should be used to check power; that no organ of government should possess absolute power.
This is because “power corrupt and absolute power corrupt absolutely”, as stated by Lord Axon and Thomas Jefferson respectively.
That each of the three organs of government should act as a watch dog over the other.
In essence, neither the executive nor the judiciary or the legislature should dominate one another and should function in cooperation with each other.
The legislature should watch and control the executive from initiating bad policy. A bill initiated by the executive must be passed by the legislature before it can become law.
The legislature can refuse to pass a bill into law, and in this way, the legislature has acted as a check on the executive.
The executive can also check legislature by refusing to sign a bill into law.
Both the executive and the legislature can be checked by the judiciary, through the declaration of laws made by both organs unconstitutional, null and void and of no effect.
Finally, the executive can control the judiciary through the appointment of judges and by this; he has acted as a check on the judiciary.