Having a summon of yours attack a green, attackable, guildmate, can make you a criminal! Not sure if this happens every time or just occasionally. Edit: Additionally, if person A is attacked by a mongbat. Person B then tames the mongbat, the tamer will flag criminal. I don't think this should be the case.
This was vaguely reported on by Apoc a while back: viewtopic.php?f=11&t=1990&p=12137 It's definitely every time. All summons making acts of aggression on guildmates will flag the caster criminal, as far as I've seen. If I recall correctly this is also the case for paralyze field and possibly other field spells. Have you tested for a time span on the taming flag? That would seem pretty out of whack but perhaps related to the window of time before a tamed monster actually goes blue?
I've gotten quite a few complaints about this from guildmates and allies. I just dismissed it as me being grey all the time from my legitimate criminal activities. . .
I think the summons/ev's aren't considered to be 'guarding you' or whatever (what I mean to say is, if they were not red, they'd be blue to you and not green.) I'm not sure if this is by design or not.