Like types, taxonomies are system-wide objects, meaning that they apply to all organizations (that is, all organizations have access to the same global set of taxonomies). You cannot restrict a taxonomy to a specific organization.

Taxonomies are also visible to all users. You can give specific users Modify or Full instance-level permissions on taxonomies, but you cannot revoke a user's View permission. All users (including guest users) can view the taxonomies defined within an instance of CentraSite.