Well the way it’s worked in the past if the country they live in won’t cooperate is, if they travel the destination country will arrest them. But that’s really just the cherry on top as far as international politics are concerned. Once a leader is officially labeled a War Criminal it’s shockingly easy to sanction them, their country, and their organizations. And basically turn their country into how Iran gets treated. So the consequences are farther reaching than just whether or not Netanyahu actually gets arrested.
Right now Israeli and American diplomats are probably planning -
A. How to prevent an adverse ruling
B. How to prevent Netanyahu from being held personally responsible so he can jettison some people and move on.
C. How to survive a worst case ruling.
In no world is Biden planning to cut Israel loose. But it could easily turn into a full blown campaign issue in 2028.