I had this situation in a recent game, and I want to make sure my call was correct. If you just want the question itself, without the setup, skip to the last paragraph.
The enemy is a high-level wizard. He had warning of the party's arrival, so he spent several rounds casting defensive spells. By the time the party approaches him, he is under the effects of Improved Invisibility, Haste, Stoneskin, Fly, Protection From Arrows, and probably a couple more spells I'm forgetting about. He proceeds to fly around the area and fire two shots per round with his wand of Lightning Bolt.
After a few rounds of this, a PC spellcaster gets a huge roll on Spot and Listen, and gets a general idea where the bad guy is. She casts Glitterdust to make him visible. The baddie then rolls a 1 on his Will save, and is therefore blinded.
To remove the blinding effect, the bad guy casts Dispel Magic on himself. But he can't choose to dispel only the Glitterdust; all magical effects on him are subject to dispelling. And, because you needn't make a caster level check against your own spell, all the defensive spells he cast on himself automatically go away. (So he begins to fall out of the sky, and is quickly turned into a pincushion.) Is this the right ruling, or did I miss a rule someplace?
The enemy is a high-level wizard. He had warning of the party's arrival, so he spent several rounds casting defensive spells. By the time the party approaches him, he is under the effects of Improved Invisibility, Haste, Stoneskin, Fly, Protection From Arrows, and probably a couple more spells I'm forgetting about. He proceeds to fly around the area and fire two shots per round with his wand of Lightning Bolt.
After a few rounds of this, a PC spellcaster gets a huge roll on Spot and Listen, and gets a general idea where the bad guy is. She casts Glitterdust to make him visible. The baddie then rolls a 1 on his Will save, and is therefore blinded.
To remove the blinding effect, the bad guy casts Dispel Magic on himself. But he can't choose to dispel only the Glitterdust; all magical effects on him are subject to dispelling. And, because you needn't make a caster level check against your own spell, all the defensive spells he cast on himself automatically go away. (So he begins to fall out of the sky, and is quickly turned into a pincushion.) Is this the right ruling, or did I miss a rule someplace?

