Qasem Suleimani’s death has been described as probably illegal by the UN special rapporteur on extra-judicial killings, Agnes Callamard, as his killing was based on the immanent threat he posed to the US. The UN has strict guidelines for such acts of preemptive self-defence to be recognised as legal, and so far the US government have not done a good job of justifying their actions. Many commentators have mentioned the lack of congressional support, which may raise political problems in the US, but without adequate justification this strike was illegal internationally also. According to US Secretary of State, Mike Pompeo, the US didn't know where or when the ‘imminent attacks’ would occur, but this apparently warranted this preemptive strike, a claim which completely undermines any argument of self-defence.
Furthermore, the failed effort to kill an Iranian Islamic Revolutionary Guard Corps financier and commander, Abdul Reza Shahlai, in Yemen on the same day shows that Soleimani’s murder was actually part of an chance assassination campaign and not a pre-emptive attack to stop a strike on the US. In this way the death of Qasem Soleimani reveals both the US' actions for what they are, an assassination campaign, and the US government's willingness to lie about it. The misrepresentation of illegal action by the US further demonstrates that this was a murder, not unfortunate, not a mistake or reasonable in any sense, as it was conveyed by US officials to the international press.