Mesirah is a proscribed action under Jewish law, consisting of informing on or turning a Jew over to non-Jewish authorities. This may not necessarily apply to reporting legitimate crimes to responsible authority, but does apply to turning over a Jew to an abusive authority, or to a legitimate one who would punish the criminal in ways seen as excessive by the Jewish community, though "excessive" punishment by non-Jews may be permissible if a precept of the Torah

Torah

Torah- A scroll containing the first five books of the BibleThe Torah , is name given by Jews to the first five books of the bible—Genesis , Exodus , Leviticus , Numbers and Deuteronomy Torah- A scroll containing the first five books of the BibleThe Torah , is name given by Jews to the first five...

has been violated.

The term for an individual who commits mesirah is a mossur.