Politics in Minutes (2016)
Liberalism as a political movement began with the ideas of John Locke, and was first put into practical form by the founding fathers of the US republic in their Declaration of Independence. They realized that liberty and rights were closely linked to limiting by law the powers of any government. A government would only be considered legitimate if it remained within the legal limitations, which they set out in a constitution.
Constitutionalism is the belief that a government’s authority derives from the constitution. This belief is, however, not as simple as it seems: the laws limiting government are themselves created by government. The implication is that the constitution represents a higher authority than that of the government, and the limitations on governmental power must be so entrenched that they are resistant to change or repeal, and enshrined in a written constitution. That is not to say that the ‘higher law’ of the constitution is fixed, but that changes to it cannot be made lightly.