The United States is not a signatory to The Hague Convention.
And the Geneva Conventions specifically deal with terrorism and those who support it.
L
“the Geneva Conventions specifically deal with terrorism and those who support it.”
...Without exempting the protections that it affords to non-combatants.
Randomly dropping MOABs in an populated city would most likely be ruled a “grave breach” by “extensive destruction... of property, not justified by military necessity”
Allies would not go for it, and whoever would authorize it would probably be pursued for war crimes for the rest of their life. It could also be used as grounds for impeachment.