The Use of Force in International Law: A Case Based Approach


The Use of Force in International Law: A Case Based Approach


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Book Chapter

Mary Ellen O'Connell, The Crisis in Ukraine - 2014, in The Use of Force in International Law: A Case Based Approach 855 (Oliver Corten and Tom Ruys, eds., 2018)

In the early morning hours of February 28, 2014, Russian armed forces moved out of their naval base on the Black Sea and into Crimea, triggering a crisis with Ukraine that continues as this chapter goes to print. The chapter begins with a detailed factual account of the Russian move into Crimea and subsequent intervention on behalf of separatist militias in Eastern Ukraine. Russia has put forward sophisticated arguments under international law to attempt to justify its military interventions in Crimea and Eastern Ukraine. On close analysis, no claim is adequate to avoid the charge of aggression. The United Nations Charter, Article 2(4), generally prohibits the use of force. Any serious violation of the prohibition is aggression. Russia can point to similar conduct by Western states from aiding the separatist Kosovo Liberation Army during in 1999 to assisting insurgents seeking to overthrow the government of Syria to Turkey’s invasion of Cyprus, allegedly under the terms of a treaty. While these and other violations of the Charter have plainly weakened the perception that the prohibition on the use of force is a peremptory norm, requiring strict compliance, peremptory norms are not modified as a matter of law by violations. Russia cannot defend its use of force against Ukraine by pointing to the violations of other states. Maintaining sanctions on Russia is important to support the international rule of law, but actually winning Russian compliance with the Charter and restoring Ukraine’s control of its sovereign territory would be more likely if other states with major militaries demonstrated the same fidelity to the Charter being demanded of Russia.



Publication Date



Oxford University Press


New York City


Ukraine, Russia, Crimea, use of force, self-defense, civil war, military intervention, humanitarian intervention, intervention by invitation, self-determination, annexation, secession, consent to the use of force, United Nations Charter Article


International Humanitarian Law | International Law | Law | Military, War, and Peace

The Use of Force in International Law: A Case Based Approach