A source of law is an entity that makes and promulgates primary legal authorities. There are two major levels of government in the United States—the federal or national government and the state governments. Primary authorities are made at the federal and state levels and also at county, municipal, and other levels.
Each level of government has branches (often three of them) that function as sources of law. For example, at the federal level, under the United States Constitution, each branch produces primary authority, as shown in this figure.
- Legislative. The U.S. Congress or the state legislature has the power to adopt statutes, though they usually require assent of the chief executive. So, for example, the President signs or vetoes the acts of Congress.
- Executive. The President or governor is the head of the executive branch, which is responsible for carrying out the laws. But the executive branch often makes laws in the form of regulatory agency rules and executive orders.
- Judicial. The courts are responsible for interpreting the laws and applying them in specific cases where there are disputes. Courts, too, make laws in the form of their opinions or decisions, which are pronouncements of common law and establish binding precedent in the interpretation of authorities from the other branches.
These sources of law and legal authorities are bound by an interlocking hierarchy of authorities.