Mr Dubnium Hassium is the former Defence Secretary of the United States of Nobelium (USN), a global military superpower. Hassium is now the Ambassador of the USN to Gallium.

In 2005, the USN and Gallium launched joint military action against Indium following a threat by Indium to invade Gallium, a close ally of the USN. An independent Commission of Inquiry established after the conflict found evidence that war crimes were committed by the USN and Gallium forces during the conflict, and that Secretary Hassium was implicated in their commission. Hassium directed the use of unmanned aerial vehicles (UAVs) to attack civilian objects. Hassium also stands accused of profiting from kickbacks after he awarded contracts for the supply of UAVs to a company controlled by one of his cousins.

One of the most serious incidents occurred towards the end of the conflict, when a UAV operator directed a drone to attack the Royal Hospital of Indium (RHI), despite an instruction from the USN and Gallium Armies to avoid damage to medical facilities. The RHI attack resulted in the deaths of two dual USN-Strontium nationals who were working for the International Committee of the Red Cross. The two victims, a married couple, had both been born in the USN, but lived most of their lives in Strontium where they raised a family, and became naturalised citizens.

Hassium is currently in Strontium as a guest of a think tank, the Institute of Policy Affairs, to present a lecture on the Indium conflict titled 'Might Actually Is Right!'. He is staying in a guest room in the Strontium Ambassador's residence. Protesters have gathered outside the Strontium embassy and the ambassador's residence and are attempting to scale the walls of the complex. Speakers at the protest include family members of the victims of the RHI attack. They are calling on the Strontium government to arrest Hassium on war crimes and corruption charges, and to support a case they have commenced in the Strontium Supreme Court seeking compensation from Hassium.

You are a solicitor engaged by family members of the victims of the RHI attack. What issues of international law will you need to address in order to advance your clients' campaign and claims?