@randahl
I did some research on how the ICC issued an arrest warrant for Putin even though Russia is not a State Party. The answer gives me hope that Trump and Hegseth could still be prosecuted in the ICC even though the USA is not a State Party.
The arrest warrant for Putin came about because Ukraine, although not yet a fully-fledged State Party, accepted the jurisdiction of the ICC. That was enough.
So, I can envision a collection of State Parties and other states accepting the jurisdiction of the ICC making the case that the USAβs war on Iran has been such a scientifically provable disaster for the environment that it amounts to a crime against humanity.