Mootness

United States federal civil procedure doctrines
Justiciability
Advisory opinions Standing Ripeness Mootness Political questions Constitutional avoidance
Jurisdiction
Subject-matter Federal question Diversity Amount in controversy Supplemental Removal Class Action Fairness Act of 2005 Personal In personam In rem Quasi in rem
Federalism
Erie doctrine Abstention Anti-Injunction Act Sovereign immunity Abrogation Rooker–Feldman doctrine Adequate and independent state ground
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The terms moot, mootness and moot point are used both in English and in American law, although with significantly different meanings.^[1]

In the legal system of the United States, a matter is "moot" if further legal proceedings with regard to it can have no effect, or events have placed it beyond the reach of the law. Thereby the matter has been deprived of practical significance or rendered purely academic.

The U.S. development of this word stems from the practice of moot courts, in which hypothetical or fictional cases were argued as a part of legal education. These purely academic settings led the U.S. courts to describe cases where developing circumstances made any judgment ineffective as "moot".

The mootness doctrine can be compared to the ripeness doctrine, another court rule (rather than law), that holds that judges should not rule on cases based entirely on anticipated disputes or hypothetical facts. These rules and similar doctrines, taken together, prevent the federal courts of the United States from issuing advisory opinions, as required by the Case or Controversy Clause of the United States Constitution.^[2]

The usage in the British legal system, on the other hand, is that the term "moot" has the meaning of "remains open to debate" or "remains unresolved". The divergence in usage was first observed in the United States and the extent to which the U.S. definition is used in U.S. jurisprudence and public discourse has ensured it is rarely used in a British courtroom. This is partially to avoid ambiguity, but also because the British definition is rarely relevant in practical cases.