[Building Sakai] Disallowing permissions for certain roles

[Branden Visser]

Hi all,

I'm wondering if it is possible by virtue of a property or !site.helper 
to globally enforce that certain roles don't have certain permissions.

For example, restrict the "Student" role from ever having 
"assignment.grade" ability, system-wide. In the assignments permission 
tab, the checkbox would then be disabled so an instructor couldn't 
enable it by mistake.

Any advice is greatly appreciated.

Thanks!
Branden