The Collaborative International Dictionary
Ne exeat \Ne` ex"e*at\ [L. ne exeat regno let him not go out of
the kingdom.] (Law)
A writ to restrain a person from leaving the country, or the
jurisdiction of the court. The writ was originally applicable
to purposes of state, but is now an ordinary process of
courts of equity, resorted to for the purpose of obtaining
bail, or security to abide a decree.
--Kent.
Wiktionary
n. (context legal English) A common law writ prohibiting the departure of a person or of property from the jurisdiction of a court.
Wikipedia
At common law, ne exeat ( Latin "that he not depart") is an equitable writ restraining a person from leaving the jurisdiction of the court or the state. The Writ may be issued to ensure the compliance by the defendant with a court order.
The full phrase is ne exeat republica (Latin "let him not go out of the republic"). The phrase ne exeat regno (Latin "let him not go out of the kingdom") has also been used in English law.
It is used in family law to restrain a person from leaving or removing a child or property from the jurisdiction. In England and Wales, however, it has been mostly replaced by passport impoundment orders. Mr Justice Mostyn said in 2012, "The writ ne exeat regno is a charming historical relic but must be regarded as an anachronism given the availability of the modern form of order".
In the United States, it is still provided for in the Internal Revenue Code at .