In a lengthy Twitter thread, Agnes Callamard said, “Outside the context of active hostilities, the use of drones or other means for targeted killing is almost never likely to be legal.”
She added that the US would need to prove the person targeted constituted an imminent threat to others, New York Post reported.
General Soleimani was killed at Baghdad airport on Friday, along with four Iranian and five Iraqi militia figures, in a strike ordered by US President Donald Trump, Financial Tribune reported.
Callamard also took issue with the justification for using drones in another country on the basis of self-defense.
“Under customary international law, states can take military action if the threatened attack is imminent, no other means would deflect it and the action is proportionate,” she wrote.
“The test for so-called anticipatory self-defense is very narrow: it must be a necessity that is ‘instant, overwhelming and leaving no choice of means, and no moment of deliberation.’ This test is unlikely to be met in these particular cases.”
Callamard noted that “an individual’s past involvement in ‘terrorist’ attacks is not sufficient to make his targeting for killing lawful”.
The French human rights expert also criticized the Pentagon’s statement about the airstrike.
“It mentions that it aimed at ‘deterring future Iranian attack plans’. This, however, is very vague. Future is not the same as imminent, which is the time-based test required under international law,” she wrote.
“Overall, the statement places far greater emphasis on past activities and violations allegedly committed by Soleimani. As such, the killing appears far more retaliatory for past acts than anticipatory for imminent self-defense.”
Callamard declared that the statement fails to mention the other individuals killed alongside Soleimani.
“Collateral? Probably. Unlawful? Absolutely,” she added.
Iraqi militia commander Abu Mahdi al-Muhandis and his son-in-law Mohammed Rida al-Jaberi were also killed in the strike.