adding state limitations to policies will make ezp throw this error:
Could not find 'Limitation' with identifier 'StateGroup_XXXXXXX'

XXXXX is the name of the state group defined in the policy.

use case:

• create a state group with two states named "go" and "stop"
• with the admin user, publish a test article and be sure that the state can be changed between "go" and "stop".
• open the article in frontend(must NOT be a legacy design) without logging in
  -> article will open ok

• create a role with just the policy:
  content read Class( Article ) , StateGroup_XXXXX( go )
• add this role to the Anonymous Users group
• clear caches, reload the article in frontend.
  -> error 500 is displayed