How to: Reject a pending save?

Gang,

I'm still only ankle-deep in the Drupal API -- and this probably shows it. BUT, I'm trying to reject a pending content save if the unchanged_node is published. I thought that 'return FALSE' would save me, but it doesn't.

Action: Content is going to be saved. (see config below)

Is there any other way to reject the save so that it doesn't happen? With this, the rejection message is shown, but the content is indeed saved. I did RTFM, but didn't find an answer...

Most gratefully,

TC

array (
'cfg_1' =>
array (
'#module' => 'workflow-ng',
'#event' => 'node_submit',
'#id' => 1,
'#weight' => '-10',
'#type' => 'configuration',
'#label' => 'DisallowEditOfPub-AllowEditUnpub-SetAuthor',
'#active' => 1,
'#altered' => false,
0 =>
array (
'#label' => 'Execute custom PHP code',
'#id' => 2,
'#type' => 'action',
'#name' => 'workflow_ng_action_custom_php',
'#settings' =>
array (
'php' => 'if ([node_unchanged:status] == \'yes\') {
drupal_set_message (\'You may not edit a published item. Change workflow first.\');
return FALSE;
}
else {
$node->status = \'no\';
$node->name = $user->user;
$node->uid = $user->uid;
node_save($node);
return TRUE;
}',
'used_arguments' =>
array (
0 => 'node_unchanged',
),
'used_php_arguments' =>
array (
0 => 'node',
1 => 'user',
),
),
),
1 =>
array (
'#label' => 'Page redirect',
'#id' => 3,
'#type' => 'action',
'#name' => 'workflow_ng_action_drupal_goto',
'#weight' => '5',
'#settings' =>
array (
'path' => 'node/[node:nid]/workflow',
'path_args' =>
array (
0 => 'node',
),
'query' => '',
'query_args' =>
array (
),
'fragment' => '',
'fragment_args' =>
array (
),
'force' => 0,
'override' => 1,
),
),
'#name' => 'cfg_1',
),
)