The fundamental law of a country refers to its Constitution. A Constitution is a set of rules and principles that outlines how a country is governed. It establishes the structure of government, defines the rights and responsibilities of citizens, and sets out the powers of the different branches of government. It is considered the highest law of the land and takes precedence over other laws and regulations. Simply put, the Constitution is the blueprint for how a country operates and is considered the cornerstone of a country's legal and political system.