A constitutional right can be a prerogative or a duty, a power or a restraint of power, recognized and established by a sovereign state or union of states. All constitutional rights are expressly stipulated and written in a consolidated national constitution, which is the supreme law of the land, meaning that any other laws which are in contradiction with it are considered unconstitutional and thus regarded as invalid. Usually any constitution defines the structure, functions, powers, and limits of the national government and the individual freedoms, rights, and obligations which will be protected and enforced when needed by the national authorities.