Editing problem

[Fabio Venturi]

Hello to the list,
I'm trying to setup a CVS server installed on Red Hat Linux
for few Windows clients using their Active Directory username and password.
So far so good... they authenticate on the system through Kerberos5 and SSH
and make checkout, commit and import without any problem.
All the users are part of cvs group and the directory is owned by cvs 
user and cvs group.
The problem is: how can i prevent users to edit files directly in the 
CVS repository
on the server with an editor through the ssh shell?
Correct me if i'm wrong, but they have to modify the code only
doing a checkout on local machine and then a commit changes.
I've tried to prevent users login with ssh, but doing so also cvs is 
blocked.
Thank you in advance for any help,
best regards,

--
Fabio Venturi