Constitutional law is a branch of law that deals with the interpretation and enforcement of constitutions, both national and subnational (such as state or provincial). It involves the study of the fundamental principles by which states are governed, including the allocation of power among different branches of government, the protection of individual rights, and the relationship between a country's government and its citizens. Constitutional law is based on the idea that the powers of government must be limited in order to protect the liberties of individuals, and it plays an important role in shaping the legal framework within which governments operate.