A Quarantined Continuum is off limits to the PPC because the creator of that continuum has forbidden fanfiction of any kind in their world. As the PPC we respect the wishes of the original Author.

In the case of Game of Thrones/A Song of Ice and Fire, George R.R. Martin has stated, quite clearly, that he is against the idea of fanfiction. He views it as a threat to the ability of Authors to make a living. While we may not agree with that reasoning (I don't), we do respect his wishes.

For more information on Quarantined Continua check the wiki.

What's His Name sealed it off.

I've never read them either, but some continuua are. *cough* Anne Rice, thank heavens, Lestat!Sue would be bad *cough*