class ActiveAdmin::PunditAdapter

def retrieve_policy(subject)
  case subject
  when nil   then Pundit.policy!(user, resource)
  when Class then Pundit.policy!(user, subject.new)
  else Pundit.policy!(user, subject)
  end
rescue Pundit::NotDefinedError => e
  if default_policy_class
    default_policy(user, subject)
  else
    raise e
  end
end