Quarantined Continuum

The author of a story can, at will, choose to block fanfiction from his or her continuum. Such a continuum is referred to by the PPC as quarantined.

The PPC itself is a semi-quarantined continuum, with prospective authors requiring Permission and no unauthorized spinoffs allowed. PPC badfic exists outside the creativity shield around HQ and does not affect the PPC canon (although this has not stopped agents tormenting their colleagues with badfic about them on occasion). Unlike other quarantined continua, the PPC is unique in that its creativity shield can be penetrated by portals, allowing PPC agents in and out to do their jobs. Unfortunately, agents traveling outside the shield can still be affected by badfic, leading to anything from insanity to being outright Sued.

Authors who have ordered their work quarantined are listed here:

If you know of an author who has allowed or banned fan fiction, please let us know.

Theory Regarding the Mechanism Behind Quarantine
Speculation exists about why some continua are quarantined and others are open to all. One such theory posits that an author is practically omnipotent in relation to his (or her) own world. Even the most powerful of god-mode Sues can't match the creativity of the omnipotent author, which makes the author intrinsically more powerful than any attacking Sue or Sue-wraith. If he chooses to block off his world from both good and bad fanfiction, an author can eliminate Sues from his continuum entirely.

Therefore, it might be that an author who has chosen to block all fanfiction from his world's canon may have effectively set up a two-way creativity shield around the canon, stopping anyone from getting in or out. An author who blocks his continuum would force any fan author who wants to write fanfiction anyway to create an entirely new world for it. This new world would be completely unconnected to the original canon. All characters within this continuum are essentially original characters, though heavily plagiarized. This applies even to crossovers where only one of the continua is quarantined; even the characters from the other continua will be original characters, since the fic has been shoved by the power of an author into its own small universe. PPCing it doesn't make much sense because the quarantine has forced the fanfiction author to effectively create a piece of (plagiarized) original fiction which cannot hurt the original canon.

That's not to say that blocking all fanfiction is the obvious choice for all authors. An open world is vulnerable to warping by badfic, but it can also be strengthened and made more detailed when good fanfiction is written in that world. An author who allows fanfiction is taking the gamble that the good will outweigh the bad. Secondary effects also protect non-quarantined continua from crossovers that include the quarantined continuum.