Unmanned drones could soon be buzzing in the skies above many U.S. cities, as the federal government green-lights the technology for local law enforcement amid widespread privacy concerns. 

The Federal Aviation Administration on Monday began to explain the rules of the sky for these newly licensed drones at potentially dozens of sites across the country. The agency, on its website, said that government "entities" will have to obtain a special certificate in order to fly the aircraft, adding that the FAA is "streamlining the process for public agencies to safely fly (drones) in the nation's airspace."

In doing so, the government is taking a tool that has become synonymous with U.S. counterterror warfare in countries like Pakistan and Yemen -- and putting it in the hands of U.S. law enforcement. 

Unlike some of the drones used overseas, these will not be equipped with missiles. They are to be used purely for surveillance. But that alone has raised serious privacy concerns on Capitol Hill and beyond. 

"Our Founding Fathers had no idea that there would be remote-control drones with television monitors that can feed back live data instantaneously -- but if they had, they would have made darn sure ... that these things were subject to the Fourth Amendment (protecting individual privacy)," Rep. Joe Barton, R-Texas, told Fox News. 

Drones have already been employed domestically. In what was described as the first case where an unmanned drone was used to arrest an American citizen on U.S. soil, a North Dakota SWAT team reportedly borrowed a Department of Homeland Security drone to monitor Rodney Brossart -- who was involved in a 16-hour standoff at his North Dakota farm over six cattle that had wandered onto his property and which he claimed as his own. The SWAT team apparently used the drone to make sure it was safe to arrest him, though his lawyer has since claimed Brossart was subjected to guerrilla-like police tactics and had his constitutional rights violated. 

Advocates, though, say the drones are a force-multiplier for local cops. 

"They're not going to be used for constant surveillance -- typically they can stay in the air for about 30 minutes, so they're only going to be used for specific missions," said Gretchen West, executive vice president of the Association for Unmanned Vehicle Systems International. 

She said the drones would help law enforcement have "more eyes in the sky to help ... assist them when they're going into potentially volatile situations." 

Lawmakers like Barton say there are "legitimate uses" for drones on U.S. soil, but that strict privacy standards will be needed. 

"It would be okay for a drone to be used in order to make sure that all the cattle on a ranch are identified on an ongoing basis. It's okay ... to survey a forest to make sure there are no forest fires. But it would not be okay if that individual who purchased the drone then decided 'I think I'll go and check and see what's going on over in my neighbor's backyard'," Rep. Ed Markey, D-Mass., said. "That would be wrong and that has to be protected against." 

Jay Stanley, a senior policy analyst with the American Civil Liberties Union, agreed. 

"We don't want a situation where every time we walk out of our front door we have to look up and wonder whether some invisible eye in the sky is monitoring us, you know, constantly," he said. "There are good uses for drones that everybody agrees with, but what we don't' want to see are drones used for constant, persistent, suspicion-less surveillance where we are all being watched for no particular reason."