Your spells can disrupt defensive spells.
Prerequisite: Ability to cast dispel magic
Benefit: A despoiling spell attempts to dispel (as described in dispel magic) any and all spell effects on the target that directly interfere with it taking effect. Use of this feat can dispel effects specifically intended to foil the spell in question (shield against magic missile, resist energy) or spells that provide general protection from magic (spell resistance). A despoiling spell uses up a spell slot one level higher than the spell’s actual level.
Feats 101. Copyright 2009, Steven D. Russell.