There are a lot of HEMS operations flying NVH in the US. I have done over 100 hours this year. The new changes to Part 61and 91 actually make is a normal operation now, asof 20 Oct 2009. There are qualification requirements, currency requirements, equipment requirements ect... It also does not discriminate fixed vs rotor nor by type of flying. If you have a Cessna 152 and or an R22 and get an authorized NVG modification done, and aquire the proper TSO NVG, you can fly NVG here with the proper training.