Drones come in a variety of shapes, sizes and capabilities that could greatly improve surveillance for law enforcement and public-safety purposes, whether it’s monitoring forest fires or providing reconnaissance for search-and-rescue operations. This technological diversity has served the U.S. military well, but it has a dark side in threats to personal privacy—and makes drones difficult to regulate.

In a subcommittee hearing that could play a crucial role in shaping drone policy—especially given that the technology is so new that current case law provides little guidance—legislators and legal experts gathered on Friday in Washington, D.C., to hash through the matter. They found a lot to disagree about, including whether existing U.S. laws—including the Fourth Amendment—are sufficient to protect privacy, or, assuming more laws are needed, whether the right frameworks should center on types of technologies or types of drone missions.

Congress has given the Federal Aviation Administration until 2015 to come up with rules governing domestic drone use. Fresh thinking is needed, as Scientific American noted in a recent editorial.

The overriding question is the impact of drone use on privacy. Although the U.S. Supreme Court has yet to hear a case specifically involving drone use, plenty of laws already on the books as well as legal precedents can guide drone use, John Villasenor, a nonresident senior fellow at Brookings Institution, said during Friday’s House Judiciary Subcommittee on Crime, Terrorism, Homeland Security, and Investigations hearing. The Fourth Amendment, for example, protects U.S. residents against unreasonable searches and seizures and requires probable cause for a court to issue a search warrant specific to a given location. Any new laws must consider the legality of a particular drone’s mission rather than the specific technology in use, he added.

Given the speed of technological change, it’s tempting for lawmakers to create frameworks that regulate the use of certain equipment, such as infrared cameras or systems that can keep drones in the air for days at a time without needing to refuel. But doing so would miss the point, said, Gregory McNeal, associate professor at Pepperdine University School of Law. It might be more effective for Congress to craft simple surveillance legislation, not specific to drones, that addresses the duration of a surveillance operation, as opposed to the platform used to do the surveillance. As an aid toward tracking correct usage, Congress could mandate that agencies employing drones catalog and publicly reveal their operations—where, when, drone type and purpose of surveillance, for example.

The American Civil Liberties Union disagreed that existing laws can manage drone use, explaining that potential privacy incursions can’t be compared with other methods of surveillance, particularly when as insect-sized unmanned aerial vehicles (UAVs) could someday act, literally, as a fly on the wall. Although drone use has been limited by cost and capability, this is changing, Christopher Calabrese, legislative counsel at the ACLU’s Washington legislative office, testified. He suggested that any new laws be based on four guiding principles:

  1. Following the principle that the accused are innocent until proved guilty, the government should not use drones for widespread surveillance of large areas in the hope of catching some wrongdoing. Instead, drone use should be subject to a warrant targeting a particular person and/or location.
  2. Information collected via drones for one purpose should not be used for other purposes and should be destroyed after it is no longer needed.
  3. Drones should not carry weapons; a drone does not have to defend itself or to apprehend someone, nor do drone operators necessarily have the training to determine when to use force.
  4. Ongoing oversight is crucial and should include feedback from the communities in which that drone is used.

Also discussed was the intersection of drones near private property. A 1989 Supreme Court decision ruled that police may use helicopters to peer into semiprivate areas—say, the backyard of a home—without first obtaining a warrant. Does this give local law enforcement the green light to deploy a fleet of drone helicopters equipped with high-definition and infrared cameras over a particular neighborhood?

Some legislators asserted that citizens have the right to privacy against drones while on their own property. “If you have private land, you have a reasonable expectation of privacy even from the air,” Rep. Jason Chaffetz (R—Utah) said.

Following this line of thinking, Rep. Louis Gohmert (R-Texas) asked whether any laws prohibit landowners from shooting down drones lingering over their property. Villasenor noted that the landowner would be liable for any injuries resulting from the takedown, but Rep. Frank Sensenbrenner (R—Wisc.) quickly noted that the hearing had run out of time and adjourned before any additional responses could be made to Gohmert’s question.

The debate’s hasty conclusion punctuated the message that the legalities surrounding drone use here are still very much up in the air.