Nothing forces users to trigger watches. They can choose to not issue the cvs edit command therefore watchers will only be notified when a commit occurs.
A way to remind users is to use cvs watch on to set file to read-only by default:
$ cvs watch on filename(s)
As before, without filename(s), it modifies all files in dir tree.
Does not change other users' working copies immediately, but file(s) will be changed to "read-only" in the future whenever: a) the module is checked out; b) a user commits the file.
In order to change from "read-only" to "read-write" the user needs to issue the cvs edit command for that file.
File will have changed back to "read-only" after it is committed.
Nothing prevents user from manually changing file with chmod.