How to squash commits in git after they have been pushed?

This gives a good explanation of squashing multiple commits:

http://git-scm.com/book/en/Git-Branching-Rebasing 

but it does not work for commits that have already been pushed. How do I squash the most recent few commits both in my local and remote repos?

EDIT: When I do git rebase -i origin/master~4 master, keep the first one as pick, set the other three as squash, and then exit (via c-x c-c in emacs), I get:

$ git rebase -i origin/master~4 master
# Not currently on any branch.
nothing to commit (working directory clean)
Could not apply 2f40e2c... Revert "issue 4427: bpf device permission change option added"
$ git rebase -i origin/master~4 master
Interactive rebase already started

where 2f40 is the pick commit. And now none of the 4 commits appear in git log. I expected my editor to be restarted so that I could enter a commit message. What am I doing wrong? How git squash commits after push?