Landmark decision

Landmark court decisions, in present day common law legal systems, establish precedents that determine a significant new legal principle or concept, or otherwise substantially affect the interpretation of existing law. "Leading case" is commonly used in the United Kingdom and other Commonwealth jurisdictions instead of "landmark case" as used in the United States.

In Commonwealth countries, a reported decision is said to be a leading decision when it has come to be generally regarded as settling the law of the question involved. In 1914, Canadian jurist Augustus Henry Frazer Lefroy said "a 'leading case' [is] one that settles the law upon some important point."

A leading decision may settle the law in more than one way. It may do so by:

Decisions in leading cases in Australia have usually been made by the High Court of Australia, although historically some have been made by the Judicial Committee of the Privy Council in London.

There is no universally agreed-to list of "leading decisions" in Canada.

One indication, however, as to whether a case is widely regarded as being "leading" is its inclusion of the ruling in one or more of the series of compilations prepared over the years by various authors. One of the earlier examples is Augustus Henry Frazer Lefroy's Leading Cases in Canadian Constitutional Law, published in 1914. More recently, Peter H. Russell and a changing list of collaborators have published a series of books, including:

Decisions in leading cases Canada are have usually been made by the Supreme Court of Canada. Prior to the abolition of appeals of Supreme Court decisions in the 1940s, most landmark decisions were made by the Judicial Committee of the Privy Council in London.

Decisions in leading cases in New Zealand were made by the Court of Appeal of New Zealand before the establishment of the Supreme Court of New Zealand, although historically some have been made by the Judicial Committee of the Privy Council in London.

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