[1]https://support.google.com/adsense/answer/16737?hl=en
[2]https://developer.chrome.com/webstore/program_policies (ctrl-f, then search for "Interfering with Third-party Ads and Websites")
Edit: Hmm, below is correct. The "single purpose" policy is pretty hard to understand, and the reason Google gave for banning it. The policy above would seem more applicable.