GPS for dummies (like, lawyers)
For the rest of us, there's a GPS Primer, courtesy of The Aerospace Corporation.
Then, a legal backgrounder from Thelen Reid & Priest LLP covers GPS/Wireless: Legal Issues Related to Wireless Navigation and Location Systems (which appears to be from 2000, but still a useful overview).
And for an interesting (and somewhat scary) rundown on GPS-related privacy, surveillance and other issues, including GPS chips embedded in cellphones (uh oh), listen in on Your Cellphone is a Homing Device, from Legal Affairs. Now we know.