What you are asking is the incorrect question or issue.
To avoid 'discretion' being used by each and every military leader of soldier, some of which might say or think a disabled opponent is 'trying to turn the capsized and burning boat over to put it out', or the 'parachuting pilot will land on the ground and start fighting on the ground', they made the RULES CRYSTAL CLEAR and NOT up to discretion and the example cited is SPECIFIC to boats and this situation that played out.
The below states clearly and undeniable that if the boat is disable, the people are NOT to be considered a threat and to be considered 'out of combat'.
So if you want to get around that you MUST explain by what authority any soldier can ignore it while substituting their own judgement.
----------
From the U.S. Military Code of Conduct
- personnel who are disabled and no longer a threat
- and survivors of maritime warfare who are “out of combat” due to ship destruction
- Enemy personnel in the water from a destroyed vessel are considered hors de combat (out of the fight)
- They may not be intentionally attacked unless they take hostile action or present a threat
- There is a duty to render assistance if feasible, consistent with mission requirements
These rules come primarily from:
- Law of Armed Conflict
(also called the Law of War — the core legal standard the U.S. military must follow)
- DoD Directive 2311.01
which makes compliance with the Law of War mandatory for the U.S. military.
- Geneva Conventions
which the U.S. adheres to and trains under as part of LOAC.
- U.S. Navy Commander's Handbook on the Law of Naval Operations
which does explicitly address people in the water after a ship is destroyed.