Public Law is the law of State, passed by the legislative organ of the government, enforced by the administrative agencies and interpreted by the courts. In other words it is a rule of conduct laid down by the State.
Public Law is a vast sub-division of Political Science. As a matter of fact, it is older than Political Science itself, as for instance the Code of Hammurabi (18th century B.C.), the Law of Moses (13th century B.C.) show. Public Law is regarded as an important, even independent, branch of Political Science. Indeed, in France and some other European countries, Political Science was once believed to be a branch of Public Law, which was collectively called Political Sciences.
Public law is divided further into civil law, criminal law, constitutional law, administrative law, Jurisprudence, International law, etc. It also consists of various systems of law, such as the Roman law, British Common Law, Islamic Law, Hindu Law, and others.