ACLs for GIT

Is anyone working on adding access control to GIT ?

I'm looking for the Subversion equivalent of mod_authz_svn.
I need to restrict read access of ITAR documents that are
scattered throughout the source tree.
This restriction would need to deny fetch of the ITAR
documents yet allow fetch of any other files.

Looking through the source code it would seem that
putting a hook call in the fetch-pack code would do it.

Thanks