Prevent users from unchecking "require password to wake computer from sleep or screen saver"
Although I have concerns about recommending this solution, you can change the access permissions for the Security (or Security &amp; Privacy) preferences pane itself so that only the Administrator account, or members of the Administrator group, will be able to open that pane.
[ᔥ Owen Linzmayer: Require Password to Wake 2005]

I want to emphasize that I have not fully tested this solution and that you should proceed with caution and do your own testing  before implementing it across an entire production environment. It seems innocuous enough, but experience has taught me that changes in places that Apple does not intend you control can sometimes have consequences.

You can set permissions for the pane using the terminal, or by navigating to the /System/Library/PreferencePanes folder:



Selecting the Security pane file:



do a Get Info using the menu, contextual menu or ⌘ + i and change the permissions for everyone to no access. You will most likely have to click the lock in the lower-right-hand corner and authenticate with your administrator password before you can edit the permissions.