How to prevent users from changing Workbench Access Section
Users can only assign a node to a workbench access section if their user or role has permissions to do so? But perhaps it gets tricky with assigning permissions to the different transitions too.

Anyway, you can lock the workbench access field on node edits, so they can't lock themselves out if you like:

&lt;?php
function MODULENAME_form_node_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  // Make sure this node type actually has workflow_access stuff setup.
  if (isset($form_state['node']-&gt;type) &amp;&amp; variable_get('workbench_access_node_type_' . $form_state['node']-&gt;type, 1) == 0) {
    return;
  }
  // Once the page has been created, don't allow changing the workbench area again.
  if (preg_match("/^node\/([0-9]+)\/edit/", current_path())) {
    $form['workbench_access']['#disabled'] = TRUE; 
  }
}