The common law began to emerge with the appearance of royal courts in the eleventh and twelfth centuries. It presented a very restrictive formalism, hence the emergence of a parallel system: equity, which calls upon morality to deliver justice.

on its side, for several centuries, the written law has been almost non-existent. It did not really develop until the nineteenth century.

The importance of jurisprudence in English law is linked to the principle of the judicial precedent that when a court decides a dispute, it must consider previous cases with similarities and necessarily adopt the same solution.

American law originated in the founding of English colonies subject to common law and equity.

In 1789, with the ratification of the American Constitution, was established a federal government as well as a legislative and judicial system comprising three organs: the Congress, the President and the Supreme Court.

The Supreme Court interprets the laws and regulations voted by the Congress and determines their constitutionality.

In 1791, the Congress ratified ten amendments to the Constitution, including Amendment X, which provides that "powers not delegated to the United States by the Constitution or which are not refused by it to States shall be given to States or to citizens ".

Thus were born the governments of each state, each with its own constitution, its own senate and chamber of representatives, and its own supreme court.

The American legal system is based on English common law, which borrows from the principle of judicial precedent, the Constitution and federal laws and regulations and, to a lesser extent, the constitutions of each State and the decisions of their respective courts. jurisdictions.