The Pentagon has deployed drones to spy over U.S. territory for non-military missions over the past decade, but the flights have been rare and lawful, according to a new report.

The report by a Pentagon inspector general, made public under a Freedom of Information Act request, said spy drones on non-military missions have occurred fewer than 20 times between 2006 and 2015 and always in compliance with existing law.

The report, which did not provide details on any of the domestic spying missions,  said the Pentagon takes the issue of military drones used on American soil “very seriously.”

The Pentagon has publicly posted at least a partial list of the drone missions that have flown in non-military airspace over the United States and explains the use of the aircraft. The site lists nine missions flown between 2011 and 2016, largely to assist with search and rescue, floods, fires or National Guard exercises.

A senior policy analyst for the ACLU, Jay Stanley, said it is good news no legal violations were found, yet the technology is so advanced that it’s possible laws may require revision.

“Sometimes, new technology changes so rapidly that existing law no longer fits what people think is appropriate,” Stanley said. “It’s important to remember that the American people do find this to be a very, very sensitive topic.”

Other federal agencies own and operate drones. The use of unmanned aerial surveillance (UAS) drones over the USA surfaced in 2013 when then-FBI director Robert Mueller testified before Congress that the bureau employed spy drones to aid investigations but in a “very, very minimal way, very seldom.”

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