Constitutional law is the body of law which defines the association of diverse entities within a state, namely, the legislature, the executive, and the judiciary.
Not all nation states have codified constitutions, though all such states have law of the land or a jus commune, that may consist of a variety of consensual and imperative rules. These may include conventions, customary law, judge-made law, statutory law, or international norms and rules. The fundamental principle by which the government exercises its authority is dealt by the Constitutional law. In some instances, these doctrine award specific powers to the government, such as the power to impose a tax and spend the money gathered from that tax for the welfare of the population. At other times, constitutional principles are there to place restrictions on what the government can do, for example, barring the arrest of an individual without adequate cause. At the time the nation came into being, the constitutional laws were formed and are based on the text of a document ratified. Some constitutions depend heavily on unwritten rules which are also known as constitutional conventions; the terms of conventions are in some cases strongly contested as their status within constitutional law varies.
Constitutional laws may often be considered second order rule making, or in other words, they are rules about creating rules to implement and exercise power. It governs the associations between the legislature, the judiciary, and the executive with the entities under its power. One of the chief functions of constitutions within this context is to specify relationships of power and hierarchies.