There are some restrictions in place to prevent high levels from walloping lower ones any time they want, actually. Normally you can only attack up and down 10% of your level, but if you attack someone higher than you on the Bounty list, or as part of War Mode, then they can attack you for up to 24 hours or until they kill you, whichever comes first. If you want to avoid their attention, don't hit them back! :)
Thanks!