A workaround for the Stylewriter 6500 is to:
1. Log in to a workstation as an administrator.
2. Go to the Finder.
3. Get Info on the StyleWriter 6500 extension, check the 'Locked' checkbox.
4. Log out.
Locking the LaserWriter driver or the LaserWriter 8 Prefs will not work, the users will get an error when trying to print. Another workaround is to downgrade the LaserWriter software to 8.3.4, which is available on Apple Software Updates.
This article can help you locate the software update mentioned here: