What legal options are open to the United Kingdom in its response to the alleged Russian assassination attempt in Salisbury? A separate piece at Just Security will discuss whether the Salisbury assassination attempt triggers the United Kingdom’s right of self-defense to use force in response. That question has garnered the most attention of legal experts. There is another strong option to consider: referring the Russian agents, potentially including President Vladimir Putin himself, to the International Criminal Court.

Prime Minister Theresa May’s team is currently preparing a package of response options. The government’s legal advisors would do well to include the Court in The Hague as a legally available option.

The basis for referring the situation to the International Criminal Court is fairly straightforward. Prime Minister May is correct that the assassination attempt involves a use of force. Whether or not it is a sufficient use of force to trigger “war” in the political sense or the right of self-defense, the use of force likely triggers an “international armed conflict” for the purposes of applying the humanitarian rules such as the 1949 Geneva Conventions and 1977 Additional Protocol to the Geneva Conventions, which the United Kingdom and Russia have both ratified.

[One of us has previously written on the concern that States may have in publicly recognizing that an armed conflict exists for fear that it will be confused with the existence of a “war” in the political sense. The U.S. Defense Department’s Law of War Manual acknowledges this political reality as a general feature of international affairs. “Government officials may deny that an armed conflict exists,” the manual explains, “to avoid an escalation in fighting and to facilitate a diplomatic resolution.” Those policy considerations naturally affect the advisability of pursuing this option, but they do not affect the legal availability of the option. ]

The attempted murder of civilians is, without a doubt, a war crime. One legal implication is that the so-called “grave breaches” regime of the Geneva Conventions would apply triggering expansive jurisdiction to prosecute Russian officials.

Another implication is that the jurisdiction of the International Criminal Court would apply as well. The United Kingdom is a party to the International Criminal Court, which allows the Court to investigate and try cases involving war crimes committed on British soil. Indeed, the Office of the Prosecutor in The Hague could take up the case herself without a referral from the United Kingdom. But a referral would help in encouraging the Prosecutor and the judges to move forward.

This route involves some legal advantages and policy risks. A referral to the Court can serve as a way for the United Kingdom to signal the strength of its conviction that Russia is responsible and to have an independent judicial institution decide the matter. It would also have a powerful symbolic effect in terms of labelling Putin and the Kremlin’s alleged actions for what they are: war crimes. Having the Court issue a war crime determination would be more powerful than just the United Kingdom or its allies doing so. Of course one significant drawback in all this is whether the UK and United States would be prepared to share the underlying intelligence pointing to Russian responsibility for the attempted assassinations.

Two other legal advantages come with the International Court. First, Putin himself would be legally exposed because the International Criminal Court does not recognize Head of State immunity. Indeed, according to the International Court of Justice, national courts would generally have to recognize such immunity while international courts do not. [I leave for others to discuss whether Head of State immunity exists for serious international crimes committed on another state’s territory.] Second, the statute for the criminal court imposes clear liability on civilian leaders who “knew, or consciously disregarded information which clearly indicated, that the subordinates were committing or about to commit such crimes” and “failed to take all necessary and reasonable measures” to stop it. The upshot here is that Putin and other Kremlin leaders would be legally exposed even if it could not be proven that they ordered or authorized the murders. What’s more, the fact that there were reportedly a series of past attempted and successful assassinations on British soil by Russian agents would help establish the case for criminal liability of the senior leadership under this provision.

A central question as to whether a referral would succeed turns on the question of “gravity” of the alleged crimes, which, pursuant to article 53(1)(c) of the Rome Statute, must be satisfied before the Prosecutor will open an investigation into a situation. There is no easy answer because the assessment of gravity is complex and involves multiple factors. As the Prosecutor has explained in her “Policy Paper on Preliminary Examinations,”The Office’s assessment of gravity includes both quantitative and qualitative considerations. …  [T]he factors that guide the Office’s assessment include the scale, nature, manner of commission of the crimes, and their impact.” (para. 61). With respect to war crimes under the Rome Statute, article 8(1) states that, “The Court shall have jurisdiction in respect of war crimes in particular when committed as part of a plan or policy or as part of a large-scale commission of such crimes.”

In November 2017, the Prosecutor at the ICC reaffirmed an earlier decision not to proceed to the investigation stage in the Comoros case which involved allegations of war crimes committed by Israeli armed forces personnel against the Mavi Marmara, a Comoros registered vessel that was part of a humanitarian aid flotilla bound for the Gaza strip. The OTP found that ten persons died and another 50-55 were injured as a result of the events on the Mavi Marmara (para. 127), but concluded that the gravity threshold had not been met for a host of qualitative reasons, including the circumstances under which the deaths occurred and the lack of evidence that they were the result of a plan or policy (para. 124).

In the UK case, the number of victims is relatively low, though if there is indeed evidence of Russian involvement in at least 14 separate deaths, the quantitative gravity becomes more important, particularly since a series of separate and discreet crimes must be considered more grave than a single criminal act. In this case, though, as distinguished from the Comoros situation, the qualitative factors likely cut towards a finding of gravity. These assassinations and attempted assassinations were plainly pursuant to a plan and policy, no doubt approved at the highest levels of government. Moreover, they occurred not in the context of a fluid battle, as with the Mavi Marmara, but were rather cold-blooded, planned, and calculated murders. Moreover, at least the latest attempted assassination appears to have potentially endangered a broad range of bystanders, and the impact on the victim community and the broader UK community has been dramatic. These factors combined support a strong though by no means certain argument that the gravity threshold has been satisfied.

There remains the matter of whether the finding of a single sufficiently grave case within a situation is sufficient. As Professor Kevin Jon Heller has pointed out, the OTP decision in the Comoros situation suggests that the OTP believes that it is. Heller argues that at the stage of deciding whether to commence an investigation, it is not sufficient to find a single case meeting gravity but that the OTP must look at the gravity of alleged crimes across the entire situation as compared to other situations. It is a compelling argument because otherwise the OTP runs the risk of being swamped by investigations; Heller’s approach offers a way to prioritize at the investigation-opening stage and limit the focus of the ICC only on those situations where the most grave crimes are occurring. However, the OTP does not seem to have committed itself to that approach and appears willing to open an investigation on the basis of finding a single case within a situation that meets the gravity threshold. If that’s the case, then the ICC could open the UK situation if it concluded that the qualitative factors here made this case sufficiently grave to meet the article 53 gravity threshold.

Whether or not the United Kingdom ultimately decides to refer the situation to the Court and whether or not the Prosecutor decides to investigate the situation sua sponte, there is still an important message here. The alleged Russian actions on British soil involve war crimes regardless of whether any state publicly acknowledges an international armed conflict exists.

(Chris J Ratcliffe/Getty Images)