You should set EDITOR to ee and use visudo if you want to use ee to edit the sudoers file, not edit sudoers file directly.
From
visudo(8):
Code:
visudo edits the sudoers file in a safe fashion, analogous to vipw(8).
visudo locks the sudoers file against multiple simultaneous edits, pro-
vides basic sanity checks, and checks for parse errors. If the sudoers
file is currently being edited you will receive a message to try again
later.