Honor Of The Duel

You strongly believe in one-on-one combat to decide a fight.
Prerequisite: Good or lawful alignment.
Effect: You must make a Will save (DC 10 + your level) to attack a creature in a square threatened by one of its other foes. A successful save allows you to attack such a creature, albeit with a -2 penalty on your attack rolls. A failed save prohibits you from attacking that creature.
Suggested Class/Race: Paladins
Source: Dragon Magazine #324 (Class Acts - Flaws For Paladins)