As the world continues to absorb the shock of the destruction of Malaysian Airlines flight MH17 and its 298 passengers and crew, there are two questions which are foremost in almost everyone's mind. What caused this disaster, and who will be criminally punished?
International law is relevant to both questions.
Under international law, Ukraine is responsible for conducting the necessary disaster investigation because the crash occurred in its territory. However, the wreckage is in an area controlled by pro-Russian separatist militias who are suspected of being responsible for destroying the aircraft.
There are also plausible reports of tampering with the crash site by the same militias.
The United Nations Security Council has therefore passed a resolution demanding a "full, thorough and independent international investigation into the incident in accordance with the international civil aviation guidelines and for appropriate accountability".
To this end, the Security Council stressed the need "for all parties to grant immediate access by investigators to the crash site to determine the cause of the incident". This last requirement is obviously addressed mainly to the separatist militias.
The International Civil Aviation Organisation, a UN agency, has accepted a Ukrainian request for assistance in the investigation.
There are already a number of known facts. There seems little doubt that MH17 was shot from the sky by a surface-to-air missile. The missile was almost certainly fired from Ukrainian territory under the control of pro-Russian militias. As MH17 was flying at 10,000 metres when it was destroyed, the missile must have been part of a relatively sophisticated military weapons system.
It seems reasonably certain that no communication was made with MH17 by the authors of the missile attack. Within minutes of the strike on MH17, there was a social media posting by a militia commander boasting that a Ukrainian military aircraft had been shot down - that posting was quickly removed when the wreckage turned out to be MH17.
Who, then, can international law hold accountable for the attack on MH17?
An international war crime can occur only in the context of an armed conflict. There is little doubt that the "protracted armed violence" in eastern Ukraine between organised pro-Russian separatists and Ukrainian government forces satisfies the definition of an armed conflict for the purposes of international criminal law.
However, criminal liability differs depending on whether the armed conflict is international or internal to one country. A somewhat wider range of conduct is criminalised in the case of international armed conflicts. We cannot yet classify the armed conflict as international in character, because Russia denies involvement in the fighting, notwithstanding Ukrainian government claims to the contrary.
At the very least, the fighting in eastern Ukraine is a non-international armed conflict.
Among the war crimes in a non-international armed conflict are "violence to life and person" of any "persons taking no active part in the hostilities", and "intentionally directing attacks … against individual civilians not taking direct part in hostilities" (Article 8 of the International Criminal Court statute).
Firing a missile at a civilian airliner en route from the Netherlands to Malaysia would certainly fall within the scope of these crimes. In this context, "intentionally" would mean firing the missile at the aircraft without taking reasonable steps to ascertain that it was not a civilian plane.
Criminal liability will certainly attach to the person who "pushed the button", and also to any person who gave the order to fire the missile.
Not only that, but the rules on "superior responsibility" mean that a war crime can also be committed by a person in a position to give orders to those who committed the crime. The crime must have been committed by people under his effective authority and control, he must have known or should have known that the crime was about to be committed, and he must have failed to take all reasonable and necessary steps to prevent the crime.
The superior will also be criminally liable if, after the crime was committed, he fails to "submit the matter to the competent authorities for investigation and prosecution" (Article 28 of the ICC statute). In other words, the superior will commit a war crime if he seeks to cover up a war crime by one of his subordinates.
International law permits Ukraine to try these offences before its own courts. Alternatively, and although Ukraine is not a party to the treaty establishing the International Criminal Court, it could make a declaration referring the missile attack on MH17 to the International Criminal Court.
Stephen Hall is a professor of international law and a fellow of C. W. Chu College at The Chinese University of Hong Kong