1. The entry into a lawsuit by a third party who, despite not being named a party to the action, has a personal stake in the outcome. See Fed. R. Civ. P. 24. • The intervenor sometimes joins the plaintiff in claiming what is sought, sometimes joins the defendant in resisting what is sought, and sometimes takes a position adverse to both the plaintiff and the defendant. Cf. IMPLEADER; INTERPLEADER. [Cases: Federal Civil Procedure 311; Parties 37. C.J.S. Parties §§ 91–93.]
2. The legal procedure by which such a third party is allowed to become a party to the litigation. — Formerly also termed (in senses 1 & 2) trial of right of property.
3. Int’l law. One nation’s interference by force, or threat of force, in another nation’s internal affairs or in questions arising between other nations. — intervene, vb. — interventionary, adj.
“Intervention may or may not involve the use of force. It is frequently possible for a powerful state to impair the political independence of another weaker state without actually utilizing its armed forces. This result may be accomplished by lending open approval, as by the relaxation of an arms embargo, to a revolutionary group headed by individuals ready to accept the political or economic dominance of the intervening state. It may be accomplished by the withholding of recognition of a new government, combined with various forms of economic and financial pressure until the will of the stronger state prevails through the resignation or overthrow of the government disapproved.” Philip C. Jessup, A Modern Law of Nations 172–73 (1949).
humanitarian intervention. An intervention by the international community to curb abuses of human rights within a country, even if the intervention infringes the country’s sovereignty.