Is my phone's GPS limited by US regulations? Apparently any GPS module made in the US and exported is classified as a munition if it is:


  Capable of providing navigation information under the following operational condition:
  
  
  At speeds in excess of 515 m/sec (1,000 nautical miles/hour);
  At altitudes in excess of 18 km (60,000 feet).
  


http://www.armscontrol.org/documents/mtcr

Would the GPS still be usable above 18 km or while travelling more than 515 m/sec?

I have a Droid Charge.
No it's not.

Commercial GPS receivers (like the one in your phone) only work below 18 km and below 515 m/sec. The rationale behind this is that this way they can't be used in ballistic missiles (yes, I'm serious.) 

In order to circumvent this you'd need to flash a different firmware to your GPS chip, if you didn't do this you're safe. No current android device ships with munitions grade GPS receiver.