Public law consists of "The laws that cover administration, constitution and criminal acts. It controls the actions between the citizens of the state and the state itself. It deals with the governments operation and structure." (Black's Law Dictionary, 2nd ed.,see The Law Dictionary, an online version of Black's 2nd.). There is also a separate body of law called Private Law which deals with individuals and their relationships. It is not part of the BA in Law core curriculum and will not be covered here.
Sources of Public Law in the United States include the Constitution, Legislation (Statutes), and the administrative rules and regulations contained in the Federal Register/Code of Federal Regulations which exist to implement the statutes.
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The Concept of Federalism
Operating in tandem with the federal government is the system of state governments. "The American federal system consists of two levels of government, each with authority over the same people but independent of the other. The national, or “federal,” government is often considered to be the “upper” level of government, in part because it encompasses the territory of all of the states, in part because of its powers under Article IV, the Supremacy Clause, of the U.S. Constitution. But the federal government is not always the hierarchical superior of the states. Rather, under the Constitution, federal and state governments are coordinate, each supreme within its own sphere, and each having a sphere in which it is supreme." (from Federalism in the Oxford Companion to American Law).
Some sources relating to a discussion of this division of powers or links to primary sources:
Federal rules and regulations are promulgated by government agencies. The authority for this agency rule-making is granted by statute and is intended to aid in the implementation of specific laws. Rules and regulations
For detailed information about administrative law and the process of rulemaking, see the following sources:
Law Library of Congress research guide on Administrative Law