To prevent guildmembers from being unwantedly drawn into a guild war, there could be a /battle command. After the guilds agreed to a war, each member of these guilds would have to apply being a 'warrior'. And if they did, there is no turning back. Once they applied, they can be attacked anywhere at any time, but those who didn't would be on the safe side. This might seem a bit unrealistic, since in RL the troops of the opposite army didn't care if you said 'Nay, I don't want to fight ye', but for the sake of fun and gameplay, it could be an option. Also, the argument of being unrealistic having to apply to be in battle doesn't hold water, as you have to agree to the war in the first place, or to a duel in general.