Constitutional law is the body of law which defines the relationship of different entities within a state, namely, the executive, the legislature and the judiciary.

Not all nation states have codified constitutions, though all such states have a jus commune, or law of the land, that may consist of a variety of imperative and consensual rules. These may include customary law, conventions, statutory law, judge-made law or international rules and norms, and so on.

Constitutional laws may often be considered second order rulemaking or rules about making rules to exercise power. It governs the relationships between the judiciary, the legislature and the executive with the bodies under its authority. One of the key tasks of constitutions within this context is to indicate hierarchies and relationships of power. For example, in a unitary state, the constitution will vest ultimate authority in one central administration and legislature, and judiciary, though there is often a delegation of power or authority to local or municipal authorities. When a constitution establishes a federal state, it will identify the several levels of government coexisting with exclusive or shared areas of jurisdiction over lawmaking, application and enforcement.

Erwin Chemerinsky (born May 14, 1953) is an American lawyer and law professor. He is a prominent scholar in United States constitutional law and federal civil procedure. He is the current and founding dean of the University of California, Irvine School of Law, which began classes in the fall semester of 2009.

Raised in a working-class Jewish family on Chicago's South Side, Chemerinsky attended the University of Chicago Laboratory Schools for high school. He then earned a bachelor's degree in communication from Northwestern University in 1975 where he competed as a debater and then attended Harvard Law School, where he was a member of the Harvard Legal Aid Bureau, graduating in 1978.

Chemerinsky taught for over twenty years at the University of Southern California Law School and at DePaul University College of Law before moving to Duke University on July 1, 2004, and then UC Irvine in July 2008.

In 1995, Chemerinsky was a commentator on the O.J. Simpson trial on KCBS-TV, KNX, and CBS News.

Chemerinsky has published six books (three of which having been printed in multiple editions), numerous articles, and a regular column on the United States Supreme Court carried by California Lawyer, the Los Angeles Daily Journal, and Trial Magazine. Chemerinsky has also argued several cases before the United States Supreme Court, including Scheidler v. NOW, Tory v. Cochran, Van Orden v. Perry and Lockyer v. Andrade.