one of the documented procedures in this installation of the ACS
naughty_content_mask_for_user   user_id
What it does:
Queries database and returns content mask for user or the system-wide DefaultContentMask if we get a NULL or no row back from the database.
Defined in: /web/philip/tcl/ad-content-tagging.tcl

Source code:

    set db [ns_db gethandle subquery]
    set content_mask [database_to_tcl_string_or_null $db "select content_mask from users_preferences where user_id=$user_id"]
    if {[empty_string_p $content_mask]} {
	set content_mask [ad_parameter DefaultContentMask "content-tagging" 0]
    ns_db releasehandle $db
    return $content_mask