Therefore, if your rules of engagement have been corrupted to allow the shooting of unarmed combatants, then ipso facto you are allowed to shoot civilians.
No need for p/a crossings out.
The rules of engagement are very clear & legally binding - no corruption.
You are not allowed to fire unless the conditions are met. Ever.
None of which amounts to permission for summary execution.
Execution is not permitted within the laws the British Armed Forces are bound by.
This is for the court to decide.
If UK soldiers don't like the idea they can be held to account for their actions, they should go and defend countries that aren't so fussy about law and order.
All personnel in the British Armed Forces have the fact that they are legally accountable for their actions drummed into them repeatedly, every year at minimum & again prior to being armed at any point at home or abroad.
Regardless of what country they are in they are bound by the international laws & Geneva Convention as well as British law - it makes no difference whatsoever if the country they are in is 'fussy about law & order'.
And (obviously) the individual soldiers, sailors & airmen have no choice about where they are sent.
My concerns would be shifting goalposts ... any trial needs to be fully aware of the situation as it was in 1972 - and not view it through the prism of today.
The soldier will be held to account IAW the rules of engagement as they were at that time, in that location.
(There are subtle differences even now depending on if you are armed in Scotland or in England/Wales, due to differences in law between the two countries).