proves impossible (because of opposition byanother permanent member of the Security Council) or impractical underthe circumstances (such as legitimate acts of self-defense under Article 51 or immediateresponses to humanitarian crises). Russia, as a majormilitary power, also may face similar tensions in the years to come. But Russia's commitment to collective security and its cooperation with the United States on military affairs probably will stimulate further bilateral efforts toundertake collective actions authorized by the SecurityCouncil (including regional initiatives).
These developments will accelerate development of the law onuse of force in the years ahead. Perhaps the three most turbulent areasof legal theory and rule-making will be those principles associated withhumanitarian intervention, illegitimate regimes, and collectivesecurity. While legal developments during the 20th centuryemphasized the development of rules on the non-use of military force, developments inthe postCold War era point toward a growing body of law and practicethat more clearly articulates and facilitates the collective use offorce to enforce international law. Thus this remains an intellectuallychallenging and potentially controversial field of law to apply to thevicissitudes of armed conflict. But we believe that state practice, customaryinternational law, and codified instruments such as the U.N. Charter are moving towards a new and promising harmony with respect to theregulation of military force.