I-law fails.

Under no scenario is Russia’s armed invasion of Ukraine legal under contemporary international law and norms.

Self-defense is the only justification for use of force against another country, according to international law. This condition is found in the  and is binding for all 193 U.N. member countries.

The charter’s only clear exception to prohibiting the use of force is self-defense, “if an armed attack occurs” against a country. Rescuing citizens who are trapped or in danger in another country is recognized as a form of self-defense. But these interventions are strictly limited to evacuating citizens, not overthrowing governments.

Nothing that Ukraine has done to date could be construed as an “armed attack” on Russia and justify any Russian claim to self-defense.

Even if Putin’s false claim that Ukraine is targeting Russian-speakers in eastern Ukraine were true, it would not justify the countrywide attacks he has unleashed.

Intervening for , such as trying to prevent large-scale loss of life or suffering, has been asserted by a few countries and activists as another rationale for use of force. But this justification has not yet been widely accepted, unless the U.N. Security Council authorizes the intervention. It did so when it authorized a U.S.-led military force in  to help prevent famine.

How is international law enforced? “Almost all nations observe almost all principles of international law … almost all of the time,” a highly respected U.S. law professor, Louis Henkin,  There is no standing international police force to enforce international law. Compliance is primarily in the hands of countries themselves.

The International Court of Justice, created by the U.N. and located in the Hague, Netherlands, decides disputes between countries, including alleged violations of the U.N. Charter. But only 73 countries out 195 have accepted the court’s jurisdiction. The U.N. Security Council also has the authority to authorize the use of force under the U.N. Charter in order to maintain international peace and security. This option is unrealistic in the situation of Ukraine because Russia has a permanent seat on the council — along with the other four permanent members: the U.S., U.K., France and China — and thus holds veto power over any decision. Finally, either the U.N. Security Council or individual countries may impose economic or diplomatic sanctions if necessary, have done. But such actions can have only an indirect impact on deterring or ending a war.

There is probably no law, international or domestic, that enjoys universal compliance. The challenge to enforce international law remains — a challenge laid bare most recently and blatantly by Russia’s invasion of Ukraine.