User_Group_Model_for_ACL.php

<!-- User model -->
<?php

    class User extends AppModel {
        var $name = 'User';

        var $belongsTo = array (
            'Group'
        );

        var $actsAs = array('Acl' => array('type' => 'requester'));

        function parentNode(){
                if (!$this->id && empty($this->data)) {
                    return null;
                }
                $data = $this->data;
                if(empty($this->data)) {
            $data = $this->read();
            }

        if (empty($data['User']['group_id'])){
            return null;
        } else {
            return array('Group' => array('id' => $data['User']['group_id']));
        }

        // Update de db "After save"
        function afterSave($created) {
            if (!$created) {
                $parent = $this->parentNode();
                $parent = $this->node($parent);
                $node = $this->node();
                $aro = $node[0];
                $aro['Aro']['parent_id'] = $parent[0]['Aro']['id'];
                $this->Aro->save($aro);
            }
            }
    }

?>

<!-- Group Model -->

<?php

    class Group extends AppModel {
        var $name = 'Group';

        var $hasMany = array (
            'User'
        );

        var $actsAs = array('Acl' => array('type' => 'requester'));

        function parentNode() {
            return 'root_node';
        }
    }

?>