Maryland Journal of International Law
The lawfulness or legitimacy of "external" intervention in the "internal" affairs of sovereign states is one of the most basic controversies in modern international law. The question arises in three separate but related forms: When is intervention lawful? When is intervention legitimate? And when should intervention occur? Discussion here will focus on the legal question, but legitimacy, morality, and brutal reality all form and sometimes trump the law. They dictate the parameters within which all legal determinations take place, including the legality of cross-border interventions. By "intervention" I mean any activity by one state or its agents that influences the actions or attitudes of another state, but particularly the threat or use of force, because force is particularly intrusive, particularly persuasive, and often particularly resented by those subjected to its power.
Since its earliest elaboration by Hugo Grotius' and Emer de Vattel international law has rested on a simple analogy and two basic premises: just as every human being should be free and equal and independent in all those things that concern her or his private interests, so too each state should be free and equal and independent in all those things that concern that state's domestic or "sovereign" affairs. As reaffirmed by the United Nations Charter, this requires both that all nations promote "respect for human rights and fundamental freedoms for all" and that outsiders not interfere in "matters which are essentially within the domestic jurisdiction of any state." More specifically, there should be no threat or use of force "against the territorial integrity or political independence of any state." This raises the questions: what rights are "fundamental"?; which actions violate a state's "independence"?; and above all, what constitutes the "domestic" or "internal" province of states?
M.N.S. Sellers, Introduction to Intervention in International Law, 29 MD. J. INT’L. L. 1 (2014).