A good friend of mine, who is a self-confessed federalist as well as attorney, would argue that the existence of drones that can spot weapons on people isn't a big deal. People who aren't doing anything illegal has nothing to worry about.
My problem with this latest development in the domestic use of drones is they are contrary to our most basic legal principle; innocent until proven guilty. Even though state and federal laws are based on British common law (notable exception being Louisiana which is based on Napoleonic law), the United States differs in that would do not believe a suspect is guilt until proven innocent (as is the case in England).
Drones snooping around in the skies presupposes guilt. The mindset is one that encourages an authoritarian stance by government officials and one of oppression by the public.
I also have a problem with an over reliance on technology that the use of drones encourages. Drones may be very sophisticated (only to become more so in the future) but they are not omniscient. They cannot tell intent. They can not determine if it is a single lone gunmen or one of many. It can only detect.
Spending more money on drones and technology means less will be spent on analyst to interpret what is being observed. If more drones are operating, they can only be as effective as the number of agents to conduct the arrest procedures. We are still a few years off (hopefully!) from Robocop, so that means manpower. What good is it to be able to see that guy in the woods is carrying a weapon if there is no one in the same zip code to arrest him?
Drones are too sexy and contractors stand to make too much money for the clock to be turned back. We have to keep asking ourselves though what all of this technology means for our quality of life.
DHS built domestic surveillance tech into Predator drones