Subversion does path-based authorization , so yes. In the related documentation there is an example with a "secret" directory. You can also use * = to remove all default access and then grant it again for a specific group, for example:
[/path/to/secret] * = @secret_users = rw [groups] secret_users=alice,bob
When someone without authorization tries to read the file, he will receive 403 Forbidden (if the repository is hosted with apache - I assume that another similar error is displayed if you use svnserve ).