More locking, sort of

[cvs]

Hi wizards.  I have what I believe to be a different variant of the
perpetual question about locking.  I have a situation where, due to
persistent problems with some hackers modifying some parts of a code
base without understanding it first, we end up with broken code much
more frequently than is justified.  A potential solution being bandied
about is to lock out write access to certain subsets of the CVS tree,
unlocking only when a change has been thought through carefully.

Obviously, there are political problems at work here; it's not
feasible to beg, borrow, steal, buy, or evolve, a better breed of
hacker. 

I've looked through the archives, explored the cvs admin and edit
commands, etc, and I don't think they're quite what I'm looking for.
It appears that what I could make it work by chmod'ing the files in
the repository, but that seems like the wrong hammer.  In a previous
life, we used CVS, and I could have sworn there was an explicit way to
lock files, effectively making them read-only, but I can't find it
now; that feature may have been removed (it was cvs 9.x, I believe),
it may have been a hacked version of cvs, or I could be
misremembering.

Any hints on how to get the effect I'm looking for would be greatly
appreciated.