Specially Protected Persons in Combat Situations (new title)

[JMA]

During a humanitarian intervention, the only appropriate use of deadly force would be for self-protection. Given that other means are available to preclude the use of deadly force, the ROE ought to be to use such means whenever possible.
I'd suggest that those involved in a humanitarian intervention be primarily (perhaps exclusively) equipped with incapaciting agents/devices. Chemical examples can be found here. Other items that are capable of causing incapitation are available. Some examples include electromuscular incapacitating devices (EMD), AKA stun guns or Tasers®, and high intensity noise generators.

As others have noted, a vigorous information operations (IO) campaign, one that pre-empts the opponent's PR strategy is also required. Such a media campaign must alert the world to the possibility of engagement by "child soldiers" and and explain the intended responses to be used should such engagements arise. The IO campaign needs to be initiated prior to deployment and continued at least until the intervention force redeploys, if not longer.

Hang on a minute. Humanitarian intervention is mere the basis/reason for the intervention. Those whose actions have led to the intervention need to be engaged in no uncertain military terms.

Humanitarian intervention refers to armed interference in one state by another state(s) with the objective of ending or reducing the suffering of the population within the first state. That suffering may be the result of civil war, humanitarian crisis, or crimes committed by the occupied nation (such as genocide). The goal of humanitarian intervention is neither annexation nor interference with territorial integrity, but minimization of the suffering of civilians in that state.

Engage and kill the perpetrators and thereby protect the people.