altering access callback in hook_menu_alter
function enge_events_menu_alter(&amp;$items){
  $items['node/%entity_object/registrations']['access callback'] = 'user_can_manage_registrations';
  $items['node/%entity_object/registrations']['access arguments'] = array(1);
  $items['node/%entity_object/registrations/list']['access callback'] = 'user_can_manage_registrations';
  $items['node/%entity_object/registrations/list']['access arguments'] = array(1);
  $items['node/%entity_object/registrations/settings']['access callback'] = 'user_can_manage_registrations';
  $items['node/%entity_object/registrations/settings']['access arguments'] = array(1);
  $items['node/%entity_object/registrations/broadcast']['access callback'] = 'user_can_manage_registrations';
  $items['node/%entity_object/registrations/broadcast']['access arguments'] = array(1);  
}


$items should be reference variable... For more information hook_menu_alter