Restricting access to certain modules in a repository

[Schlitz]

I am using pserver to authenticate users that don't have system accounts on
the server machine.
I have all modules in a single repository.  I want some of these modules not
to be available at all (not even check out permission) to some users.

I have a basic system 'cvsuser' user that is used in the passwd file as the
system user name for all users.
Because the repository is on some kind of network-attached drive (which I
have no knowledge of), there are (so the sysadmins tell me) complications
that prevent us from using unix group permissions facilities to control
access to the different modules in my repository.

Is there any way to control all access to some modules in a repository in
this scenario?  I use scripts to control commit permissions by user name on
a per-module basis, and do the same for tags, etc....is there a similar
facility that can be used for checkouts, or some other technique?

Thanks!