Disabling node editing after first node flagging
D7, no need of rules, place this code in your MODULE

function MODULE_node_access($node, $op, $account) {
 if ($op == 'update') {
  $flag='';
  $flag = flag_get_flag('YOUR_FLAG_MACHINE_NAME');
            if ($flag &amp;&amp; $flag-&gt;is_flagged($node-&gt;nid, $GLOBALS['user']-&gt;uid)) {
  return NODE_ACCESS_DENY;
    }
  }
}


done, enyoy.