Ahh sorry you're running SBE, just caught that.
This option is not available in SBE:
https://www-secure.symantec.com/connect/forums/how-prevent-users-uninstalling-sep-121-sbe
The best you can do is follow this article:
How to block a user's ability to disable Symantec Endpoint Protection Small Business Edition on Clients
http://www.symantec.com/docs/TECH172434