Why is "engaging an insurgent" now murder?

[Thatcherite]

http://www.bbc.co.uk/news/uk-19918398
It's going to be a little tricky if our troops are not allowed to shoot the enemy!
I know, they can use firm but fair language. "I say chaps, would you mind awfully not shooting at us as we have some strange rules of engagement that means we are going to have to put you all in detention". That'll sort the Taliban! Being a soldier is almost as bad as being a school teacher these days.

[Gromit]

Turns out one of our 'heroes' filmed the murder on his mobile phone and put it on his laptop.. D'oh!!!

[DaisyNonna]

The Rules of War. An oxymoron perhaps? War is not a B****y board game.
People are dying. People who are not fighting, some old people, women, children. If you are not my friend then you are my enemy. Enemies deserve to die. Do we believe this? If governments can agree on the rules of war they should be able to agree on the rules of peace.