There appears to be an insane loophole in the new FAA regs on drone registration. Apparently, non-citizen operators can't register their drones. The FAA, by law, cannot register aircraft belonging to foreigners. They can issue a certificate of ownership, but that seems to be completely voluntary. So I guess any non-citizen terrorists wanting to use a drone can go right ahead without worrying that they are breaking the law!
Here;s the FAA's FAQ on this:
UAS Registration Q&A