What protects natural rights by imposing restrictions on those in power?

The concept that protects natural rights by imposing restrictions on those in power is known as a "constitution" or the rule of law. A constitution is a set of fundamental principles or established precedents according to which a state or other organization is governed. These rules together make up, i.e. constitute, what the entity is. In the case of countries, this defines the fundamental political principles, and establishes the structure, procedures, powers, and duties, of a government. Most constitutions also attempt to define the rights of individuals, including a bill of rights. A written constitution is often codified as a written document, but some countries like the United Kingdom have an uncodified constitution formed from statutes, case law, convention, and various other sources.

The rule of law implies that every person is subject to the law, including people who are lawmakers, law enforcement officials, and judges. In this context, it stands in contrast to an autocracy, dictatorship, or oligarchy where the rulers may be held above the law. The rule of law ensures that laws are clear, publicized, and stable; are applied evenly; and protect fundamental rights, including the security of persons and property. The separation of powers, often found within a constitutional system, further supports restrictions on those in power by dividing governmental responsibilities into distinct branches to limit any one branch from exercising the core functions of another.