Is Russia's invasion justified? I'll lay out the competing arguments and what international law says.
Russia's full-scale invasion of Ukraine, launched on 24 February 2022, is presented as justified by Russia and as unjustified and illegal by Ukraine and the majority of the international community. How it is assessed depends on what framework is used - Russia's stated security and humanitarian rationale vs. international law.
1. Russia's Stated Justifications
In his 23-24 February 2022 address announcing a "special military operation," President Vladimir Putin claimed that intervention was necessary to "protect people who have been subjected to abuse and genocide" by the Ukrainian government and to "protect Russia and our people". The stated aims included "the demilitarisation and denazification of Ukraine".
More specifically, Russia has advanced several arguments:
•Protection of Donbas populations: Russia claimed the Donetsk People's Republic and Luhansk People's Republic, which it recognized as independent states two days before the invasion, had requested assistance and that Russian-speakers in the Donbas faced genocide and abuse.
•Self-defense under the UN Charter: Russia has argued that its use of force is lawful under Article 51 of the UN Charter, which preserves the right to individual and collective self-defense against an armed attack.
•Security concerns about NATO: Another significant component was NATO expansion. Putin portrayed NATO's eastward enlargement as an existential threat to Russia's security. Russia has consistently argued that NATO's eastward expansion threatens its national security and that Ukraine joining NATO would eliminate a strategic buffer. Russia demanded guarantees Ukraine would never join NATO and that NATO roll back military presence in Eastern Europe.
•Historical and political claims: In speeches on 21 February 2022, Putin questioned Ukraine's legitimacy as a state and cited historical grievances.
2. Evaluation Under International Law
The UN Charter, a central document of international law, sets the conditions under which states may legally use force.
•Prohibition on the use of force: Article 2(4) provides that all members "shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state". A similar formulation is that states must not use military force against other states except defensively or if the UN Security Council authorises it.
•Narrow exceptions: There are only two narrowly defined exceptions to this prohibition: action in self-defence or under authorization of the UN Security Council. The Charter likewise states the only two exceptions are self-defense and an authorization by the Security Council.
Most international law experts have concluded the invasion violated these principles and rejected Russia's legal justifications:
•Self-defense argument rejected: Experts argued Russia cannot rely on self-defense because Ukraine had not threatened or attacked any other nation, and because Donetsk and Luhansk are not recognized as separate states under international law, so collective self-defense does not apply.
•Humanitarian / genocide argument rejected: Experts have also rejected the argument that the invasion is justified to protect Russian-speakers. Some noted the legality of humanitarian intervention is heavily disputed. In any event, the humanitarian justifications are widely perceived as a pretext and are unsubstantiated by any evidence that Ukraine has committed acts that could amount to genocide. Scholars described Putin's allegations of genocide and comparison of Ukraine to a Nazi state as baseless.
•Security concerns do not create a legal right to invade: While Russia has security perceptions that can be examined, analysts note that these security concerns do not create a veto right under international law over a sovereign state's foreign policy choices.
•Alleged treaty violations: The invasion has also been described as violating other agreements Russia is party to, including the 1975 Helsinki Final Act, in which the USSR promised not to violate the "territorial integrity" of other signees, and the 1994 Budapest Memorandum, in which Russia agreed "to respect the independence and sovereignty and the existing borders of Ukraine".
Because it violates the UN Charter and is more than a minor border incursion, legal experts qualified the intervention as a crime of aggression under Article 8bis(1) of the Rome Statute, defined as an act of aggression which constitutes a manifest violation of the Charter.
Comparisons by Russia to Western interventions such as Kosovo, Iraq, or Libya have been dismissed by many legal scholars as irrelevant on the principle that one illegal act does not make a different act legal.
3. International Response
•At the UN Security Council, Russia vetoed a resolution that would have called for it to cease its attack.
•At the UN General Assembly, Resolution ES-11/1 adopted on 2 March 2022 deplored Russia's invasion of Ukraine and demanded a full withdrawal of Russian forces. It passed 141-5 with 35 abstentions, with only Russia, Belarus, Syria, North Korea and Eritrea voting against. The resolution demanded Russia "immediately, completely and unconditionally withdraw all of its military forces from the territory of Ukraine within its internationally recognized borders".
Summary
•From Russia's perspective, the invasion is justified as a defensive, protective action for Russian security, for Russian-speaking populations in the east, and to prevent NATO encroachment.
•From the perspective of international law as interpreted by the UN General Assembly, the International Court of Justice proceedings, and the majority of international legal scholars, the invasion lacks a valid legal justification under Article 51 or humanitarian intervention doctrines, constitutes a violation of Article 2(4) of the UN Charter, and is therefore considered an illegal act of aggression.
Whether the invasion is seen as justified ultimately depends on whether primacy is given to Russia's national security narrative or to the prevailing interpretation of sovereignty and the prohibition on the use of force in international law.