Non-statutory law refers to the sources of law other than statutory law. Its authority rests not on legislation passed by Parliament and/or Administration and eventually codified, but rather tradition, custom, and especially precedent. It is recognized within the United States Constitution as being essentially inviolable; however, as customs and traditions change and evolve, the common, non-statutory law must change and evolve with them , and occasionally be amended by statute.

The huge collection of "law books" seen in most law offices is for the most part not a compilation of statutory law; in most U.S. states, for example, the collection of currently valid and enforceable statutory law would take up one moderately-sized bookshelf. The rest are primarily the records of past trials used as precedents. An important aspect of the common law (and, indeed, of statutory law as well) is the concept of stare decisis, a Latin term meaning "let the decision stand". In other words, once a decision has been rendered in a past case regarding a law in question or one very similar to it, in absence of any new reasoning or evidence, the law should be interpreted the same way again. In the United States, generally such new reasoning comes from new decisions of the Supreme Court of the United States, which sometimes reverses the decisions of past Supreme Courts. Perhaps the best example of this is the case of Brown v. Topeka Board of Education, where changes in society occurring between 1896 and 1954 dictated that the Court override the clear precedent, Plessy v. Ferguson. Brown became the basis for a new body of non-statutory law arising from it, even though it was not a new piece of legislation nor a new constitutional amendment but rather a re-interpretation of an existing constitutional amendment.

Thus, the two main types of non-statutory law are the common law of tradition and custom, and the similar, related concept of legal precedent. Both are very important, but, in practice, neither is inviolable.

Law

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