What principle ensures that government power is limited and defined by law?

The principle that ensures government power is limited and defined by law is constitutionalism. This concept revolves around the idea that the authority of the government is constrained by a constitution, which outlines the framework for governance and the rights of individuals. Constitutionalism establishes a system in which laws govern the actions of both the government and its citizens, ensuring that power is not exercised arbitrarily and is instead bound by established legal norms.

This principle is foundational to the functioning of democracy, as it seeks to protect individual liberties and prevent the concentration of power. By adhering to constitutionalism, governments must operate within the boundaries set by the constitution, providing a legal framework that promotes accountability and transparency. This is crucial in the context of the rule of law, emphasizing that all individuals, including those in power, are subject to the law.

Other options may represent important aspects of governance, such as allowing citizens to express their will (popular sovereignty), delineating responsibilities among different branches (separation of powers), or instituting mutual restrictions among branches (checks and balances), but they do not specifically focus on the limitations of government power through a legal framework as effectively as constitutionalism does.