Saw this interesting question on the forums today and wanted to share one solution you may find useful at some stage:
This basically removes all access to the Appearance menu in the WordPress dashboard so admins cannot access any themes and make any changes whatsever.
The toolbar menu will still display a link to the themes page however this is the message that is displayed when that menu link is clicked:
It removed the Genesis Theme Editor too.
I tried this by adding the code into functions.php and it worked. I then removed the code and it has caused the Appearance menu to not reappear. I cleared all cache, logged out/in, and it still doesn’t come back. Any ideas on what to get the Appearance menu to reappear?
Change remove to add and add the code again.