I don't mean to interrupt this highly technical discussion but I'm hoping nobody will object to me digressing back to the original question. It seems that I've been one of many people who asked this question officially. The answer has now been given by the United States, in terms that I was expecting though I still had to ask anyway!
Here is the answer :-
U.S. Policy Statement Regarding GPS Availability, March 21, 2003
* The United States Government recognizes that GPS plays a key role around the world as part of the global information infrastructure and takes seriously the responsibility to provide the best possible service to civil and commercial users worldwide. This is as true in times of conflict as it is in times of peace.
* The U.S. Government also maintains the capability to prevent hostile use of GPS and its augmentations while retaining a military advantage in a theater of operations without unduly disrupting or degrading civilian uses outside the theater of operations.
* We believe we can ensure that GPS continues to be available as an invaluable global utility at all times, while at the same time, protecting U.S. and coalition security requirements.
I would like to publicly acknowledge and thank CASA for obtaining this statement for me.