From World War Three by Mistake:
After being launched, a Minuteman III cannot be remotely disabled, disarmed, or called back. From the very beginning of the Minuteman program, the Air Force has successfully fought against adding a command-destruct mechanism, fearing that an adversary might somehow gain control of it and destroy all the missiles mid-flight. “Once they’re gone, they’re gone,” an Air Force officer told “60 Minutes” a few years ago.
It's nice to see that, at least at some levels within the US government, they're aware of the risks of backdoors.