Please specify if you mean write access or read access.
Gitolite's per-branch stuff works only for write access. It
doesn't work for read access because git itself does not
support making that distinction.
The normal way to do that is to use separate repos. Gerrit
Code Review does support it, because they don't use the
normal git engine; they have their own Java based git engine
(as well as their own sshd, etc).
--
sitaram