Disable "encrypt before storing in your mail file" preference

In a Notes 6.5.x on the Mail tab of the File-Security-User Security dialog box there is an option for the user to enable/disable “When receiving unencrypted mail, encrypt before storing in your mail file”.

There does not appear to be a way to control this parameter from a policy settings document.

Is there away to prevent the users from being able to check/uncheck and enable/disable this preference?