SonataUserBundle/Security/Authorization/Voter/UserAclVoter.php

<?php
namespace Sonata\UserBundle\Security\Authorization\Voter;

use FOS\UserBundle\Model\UserInterface;

use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
use Symfony\Component\Security\Acl\Voter\AclVoter;

class UserAclVoter extends AclVoter
{
   /**
    * {@InheritDoc}
    */
   public function supportsClass($class)
   {
       // support the Object-Scope ACL
       return is_subclass_of($class, 'FOS\UserBundle\Model\UserInterface');
   }

   public function supportsAttribute($attribute)
   {
       return $attribute === 'EDIT' || $attribute === 'DELETE';
   }

   public function vote(TokenInterface $token, $object, array $attributes)
   {
       if (!$this->supportsClass(get_class($object))) {
           return self::ACCESS_ABSTAIN;
       }

       foreach ($attributes as $attribute) {
           if ($this->supportsAttribute($attribute) && $object instanceof UserInterface) {
               if ($object->isSuperAdmin() && !$token->getUser()->isSuperAdmin()) {
                   // deny a non super admin user to edit or delete a super admin user
                   return self::ACCESS_DENIED;
               }
           }
       }

       // leave the permission voting to the AclVoter that is using the default permission map
       return self::ACCESS_ABSTAIN;
   }
}