I don't think this belongs here, this seems more like extension developer documentation that belongs in the docstrings of the `IAuthFunctions` plugin interface, which autodoc pulls into the _Writing Extensions_ chapter. I think the audience for this chapter, is just sysadmins who are setting up a CKAN site. You _do_ need to mention `IAuthFunctions` on this page, but just put in a cross-reference to the other page, don't give any details (don't even mention function overriding). Just something like:

    If you want to customize CKAN's authorization behaviour further, you can do this from a CKAN plugin using [IAuthFunctions] 
    plugin interface.

Also, mention of `check_access()` seems only relevant to CKAN core devs, not even extension devs? That probably belongs on the [CKAN Code Architecture](http://docs.ckan.org/en/latest/architecture.html) page (if it's not there already)