Question on Mob Factions

Hey guys i got a quick one. Im tinkering with races for mobs. Elves Dwarves etc
I can make them attack other factions by setting the
AItargetselector:
- 0 OtherFactionMonsters
but i want to exclude some

lets say the dwarfs and elves have a peace treaty going on. How do i do it so they dont attack eachother but they will beat up the nasty orcs and weak humans?

Thanks in advance