[quote=@harinezumikouken]
The mission is to just 'take care' of the Bandits, right? I mean, wouldn't it be unjust to just outright execute the unarmed and harmless Bandits? Wouldn't it say more for the Iron Roses if they kept them as prisoners to be put to fair trial or even put them through a rehabilitation process to make them into functioning members of society?
[/quote]

These bandits have:
1) Sacked and looted villages. There's no prize for guessing what happened to the inhabitants.
2) Killed the forces sent to defeat them before.
3) Used a dying man as a messenger, and another injured one as bait. Probably done this sort of thing before.
4) Tried to kill [i]us[/i].

Whilst there might be cause for a trial afterwards, [i]taking prisoners right now is the worst time to do it.[/i] Also, would it be just? Well... yes, in the perfectly legal sense; they're outlaws and we were tasked with dealing with them. Also why I don't think any of them are getting away with a slap on the wrist... or axe on the wrist.

And in the 'don't keep enemies at our back' one.