not quite this as stated:

from JMA
... if the bad guys supplying the reason the humanitarian intervention are all 20-30 year olds I suppose a shoot on sight / shoot to kill policy would be fine?
although one might end up with something like that policy in practice.

To get to a "shoot anyplace, anytime" rule (a "status" ROE), one has to have:

1. A designated hostile force. Not that hard to pass that step if the hostiles are at least semi-organized (LRA, WSB, etc.)

2. The person whacked must be positively identified (PID in US ROE jargon) as a member of (part of) that hostile force. Passing that step is more difficult with irregular forces, especially under the Geneva Additional Protocols requiring the "whackee" to be "directly participating" in the armed conflict when whacked.

So, in many irregular warfare situations, PID comes about only because the person presents a hostile, armed threat - and the rule becomes just about the same whether one is under the Laws of War or the Rule of Law.

That is the theory - repeat, theory.

I can't see anything more strict than probablilities playing a role in reality - unless the soldier has a strong death wish. Is it more probable than not that the person in your sights is the enemy ?

What is the real "standard" for employing less definite tactics (than a person in your sights); such as, recon by fire. A probability (possibility ?) that enemy might be in that patch of thorn bush ? Or, for that matter, H & I arty, which is even less definite ?

Combat does not seem a good place to employ complicated legalisms.

Regards

Mike