Board Thread:Questions and Answers/@comment-31516341-20170619120207/@comment-918376-20170626203238

Because they're doing a job, and their job states that they are required to punish those who commit violent acts inside noncombat zones. It's like how people who kill in self-defense can still be charged for murder (or manslaughter?) even if it was done in self-defense. There's no inconsistency at all, since we don't actually meet a Royal Guard in the novels until volume 6.

Royal Guard rules are also bizarre on their own, because on one hand the novels stated they lock people in prison if someone misbehaves in a noncombat zone (which seems to be the only situation in which they appear), but then it's also stated that they just kill players who are involved in combat. I figured that Royal Guards lock people in prison unless the person fights back, after which they would be killed (would be consistent with the LH official manga), and the WWB manga did its own thing like usual. But then volume 2 stated that anyone who breaks the rule would meet death, so :/