Chapter 90:

even a simple Obliviation will stretch the edge of your current stamina. It is a dangerous art, illegal to use without Ministry authorization, and I would caution you not to use it under circumstances where it would be inconvenient to accidentally erase ten years of someone's life. I wish I could promise you that I would obtain one of those highly guarded tomes from the Department of Mysteries, and pass it to you beneath a disguised cover. But what I must actually tell you is that you will find the standard introductory text in the north-northwest stacks of the main Hogwarts library, filed under M.

So there is no defense against Obliviation that Voldemort could have prepared for himself?

I confess I expected paranoid-Moody thinking from Harry, not Far-mode Good thinking. The stakes are so high that anything other than ruthless pragmatism feels insane to me.