Changing audit settings in GPO will not change audit settings in Local security policy once audit is set in GPO

I created a GPO to enable Success and Failure to log all System events and to log all Privilege use. Once rab gpupdate /force, my Local Security policy changed to match the GPO. Fine, no problem. I go back to the GPO and tell it to no longer audit system events. Ran gpupdate again and the Local Security policy did not change to reflect the new settings in the GPO. Why not?

Thanks

Sean