Would this work?

[Angcuru]

Since healing spells hurt the undead, if you cast True Ressurection on a lich, would it die?

 

[DanMcS]

Heal, on the other hand, would seriously work him over.

 

[Cedric]

I would have the Lich to make a will save or be resurrected and returned to life.

...It is a 9th level spell afterall, besides, wouldn't that just be cool!

Cedric

 

[s/LaSH]

Before concluding, I advise looking at this: http://enworld.cyberstreet.com/showthread.php?s=&threadid=46121, as it deals with the metaphysics necessary to come to an educated conclusion.