Interestingly just nine days ago someone here shared a link to the US's Law of War manual for military personnel. It's pretty good for what it is. Since countries base this stuff on the same international treaties they've all signed, it's a guide to Israel's conduct during war (or just about anyone's) as well as the US's.

https://news.ycombinator.com/item?id=46147605

https://media.defense.gov/2023/Jul/31/2003271432/-1/-1/0/DOD...

The question of whether what Israel did with the pagers was legal is not really controversial, or rather, it's not unclear what the law is. Find out the exciting answer in 6.12.4.8 Booby-Traps and Other Devices in the Form of Apparently Harmless
Portable Objects Specifically Designed to Explode. (spoiler alert: of course what they did is illegal)

In case you were wondering what the big deal was the other day about the US bombing shipwrecked "narco terrorists" there's 7.3 RESPECT AND PROTECTION OF THE WOUNDED, SICK, AND SHIPWRECKED.