Under the Federal Aviation Administration Modernization and Reform Act of 2012, signed into law by President Barack Obama in February, the FAA is required to of unmanned aerial vehicles by a wide range of organizations including private hobbyists.

The law requires the FAA to make rules pertaining to the safe operation of private, commercial and government drones over U.S. airspace. Under the law, law enforcement authorities and emergency services will be allowed to start using small drones as early as next month.

Over the next few years, thousands of unmanned aerial vehicles of varying sizes and capabilities are expected to be in use over U.S. skies for applications such as fugitive tracking, traffic management, crop monitoring, land management, news reporting and filmmaking.

Privacy and civil rights groups have expressed alarm over the privacy implications of widespread drone use especially by government and law enforcement agencies. They maintain that drones equipped with high-tech cameras and listening devices will be able to conduct unprecedented surveillance of civilians.

In a letter sent Thursday to the FAA acting administrator Michael Huerta, U.S. Reps. Edward Markey (D-Mass.) and Joe Barton (R-Texas) expressed similar concerns.