The setFactionAttackableBelow native AI script function sets the group as being attackable (or not) by players having their fame matching the specified condition. If player fame for Faction is below specified Threshold, the bot will be attackable by that player or not depending on Attackable parameter, 0 meaning not attackable, 1 meaning attackable.
()setFactionAttackableBelow(faction: s, threshold: f, attackable: f) // setFactionAttackableBelow_sff_
()setFactionAttackableBelow("TribeMatisianBorderGuards", 0, 1);
This example code makes the group attackable by players with negative tribe_matisian_border_guards fame.