Offline Validation Rule is not triggered when editing the in-line Territory Field (TSF) control on Account in CRM iRep.
Generic data entry for most objects in CRM is currently supported. Generic data entry is defined as data entry using the standard editing or saving features for an object.
For example, editing the in-line TSF control on an Account does not trigger Validation Rules. Editing through the related list triggers Validation Rules.
Use the standard editing or saving features for an object instead of using in-line editing.
CRM Help Documentation: Offline Validation Rules