To briefly recapitulate our examination of mistake of fact when using lethal force in various sub-fields of international law: such a doctrine is, in its purely subjective form, black letter law in international criminal law. It is also established (even if not labelled as such) in international human rights law and (somewhat less clearly) in international humanitarian law. Both IHL and IHRL would however require the mistake to both honest and reasonable to be able to preclude liability. Both IHL and IHRL contain explicit precautionary and prophylactic rules whose role, in part, is to determine the bounds of reasonable and hence permissible error (e.g. with respect to target verification).
As we have seen, the mistake of fact question is most fraught in the jus ad bellum. That said, as a formal matter, even if one thought it to be desirable, it would be difficult to argue that a jus ad bellum-specific mistake of fact doctrine was customary law. I cannot think of any state but the US that has invoked such a doctrine, even implicitly. (Any such examples known to readers would be most welcome.) And when the doctrine was invoked, as with the Iran Air Flight 655, it certainly did not attract widespread acceptance by other states. There is enough ambiguity in state reactions to the downing of that aircraft, especially in the atmosphere of the Cold War, that one cannot categorically exclude that such a rule could exist. But it seems unlikely that it does. And if it does, it cannot be the purely subjective one from ICL, which would be even more inappropriate in the jus ad bellum context than in IHL and IHRL.
Bearing all this in mind, let us turn to the downing of Ukraine International Airlines Flight 752 over Tehran, which is as we have seen eerily reminiscent of the shooting down of Iran Air Flight 655 by the USS Vincennes. There are many parallels between the two incidents, not least that they both involve the same two states, if on different sides of the story, and that both cases raise questions of mistake of fact. What is very different is the wider context – the Cold War warped anything it touched. And I think it fair to say that the socializing effect of international law is somewhat greater today than it was then.
Thus, states like Ukraine and Canada have already used legal language vis-à-vis Iran. President Zelenskyy stated that:
Iran has pleaded guilty to crashing the Ukrainian plane. But we insist on a full admission of guilt. We expect from Iran assurances of their readiness for a full and open investigation, bringing those responsible to justice, the return of the bodies of the dead, the payment of compensation, official apologies through diplomatic channels.
Prime Minister Trudeau similarly stated that ‘Iran must take full responsibility’ for its actions.
And this is exactly what Iran should do. It shouldn’t just listen to these other states invoking its responsibility. It should listen to the voice of its own ambassador, when he was speaking in the Security Council chamber to reject the US self-defence justification for shooting down IR 655:
We believe that a responsible Government, under the present circumstances when it has caused the destruction of a civilian airliner and its 290 passengers, must urgently take three steps: It must apologize to the families of the victims and to the peoples and the Governments concerned ; it must accept full responsibility for the downing of the airliner and offer reparation on the basis of its legal and moral liability; and it must reassess and revise policies which led to the downing of the plane and the murder of its innocent passengers. (S/PV.2821, 6)
An equally intriguing parallel is that with McCann. Indeed, I would argue that it is precisely human rights law – largely absent from the discussions of the destruction of IR 655, aside from a single reference by (of all people) the ambassador of Syria – that is the body of law that best fits the downing of the Ukrainian airliner. The gravest violation of international law here is not that of the Chicago Convention, but that of the human right to life, the wrongfulness of which could, unlike with the Chicago Convention, never be precluded by jus ad bellum self-defence.
Just like the SAS soldiers in McCann, the Iranian air defence officers most likely honestly believed that they had to act to deflect a threat to human life. Just like in McCann, they were wrongly told that such a threat was certain – that US cruise missiles would be incoming. Just like in McCann, they had little time to deliberate. And just like in McCann, the violation of the right to life stems not directly from the soldiers’ decision to use lethal force, but from systemic background failures of higher Iranian authorities.
Had Iran closed its airspace for civilian traffic that evening, knowing full well that hostilities with the US might easily escalate, the plane would never have been shot down. Had Iran properly coordinated its air defences with civilian air traffic control, the plane would never have been shot down. Had Iran properly trained its forces at various levels, the plane would never have been shot down. Thus, even if Iran’s mistake of fact that resulted in the destruction of the aircraft was honest, it was not reasonable, and as such it would bear state responsibility for violating the victims’ human rights. And that violation is compounded by the initial attempts of Iranian authorities to obstruct the investigation and cover up the cause of the crash, from which they have thankfully desisted, but which nonetheless resulted in a violation of the positive obligation to effectively investigate unlawful deaths.
This is therefore how Iran should frame the reparations it provides – not as ex gratia charity payments, not (solely) as compensation due to states such as Ukraine or Canada, but as just satisfaction to those individuals whose rights it violated. In doing so, Iran should compensate its own nationals in the exact same way as it compensates foreigners, as equals in dignity. And it needs to provide sufficient assurances to the international community that a mistake such as this one, honest though it may have been, will never be repeated.