Intervention (law)
（重定向自Intervenor）
In law, intervention is a procedure to allow a nonparty, called intervenor (also spelled intervener) to join ongoing litigation, either as a matter of right or at the discretion of the court, without the permission of the original litigants. The basic rationale for intervention is that a judgment in a particular case may affect the rights of nonparties, who ideally should have the right to be heard.