When drone operators try to fly their birds not for fun but for profit, the Federal Aviation Authority has reminded them — sometimes with fines, sometimes with phone calls — that its guidelines do not permit the commercial operation of drones in the U.S.

On Thursday, the National Transportation Safety Board dismissed one such fine, which the FAA slapped on drone photographer Raphael Pirker in 2012.

"It does mean that if you have this kind of aircraft [the FAA] is not going to be in a position to fine you," Ryan Calo, professor of law at the University of Washington, told NBC News. He expects the FAA will act to close the gap in their regulation ability, or file an appeal. "I don’t think it’s time to let a thousand drones fly, it’s time to watch and see how the FAA reacts," he said.

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In 2011, Pirker, a skilled hobbyist and photographer, flew his Zephyr II craft over the University of Virginia campus and recorded photo and videos, which he sold to the university. In 2012, the FAA fined him $10,000, citing a number of violations including operating the aircraft in a reckless manner.

Pirker and his attorney, Brendan Schulman, filed a motion with the NTSB to dismiss the penalty, questioning the FAA's authority to legally regulate drone technology. In a ruling Thursday, the NTSB granted their request to dismiss the fine.

"[A]t the time of Respondent's model aircraft operation, as alleged herein, there was no enforceable FAA rule or FAR Regulation, applicable to model aircraft or for classifying model aircraft as an UAS (unmanned aircraft systen)," NTSB Administrative Law Judge Patrick Geraghty explained in his decision.

The NTSB serves as the "court of appeals" for challenging civil penalties assessed by the FAA.

According to the FAA's existing guidelines, private operators may fly their drones recreationally and organizations such as police departments and universities must seek and be granted permission to test or fly theirs. Though the FAA has been tasked with paving the way for companies like FedEx or Amazon to one day fly their delivery birds safely, the guidelines are one reason most drone operators in U.S. skies are hobbyists. But Thursday's result hints at a possible shift in the winds.

"I think this decision will be of great interest to other commercial drone operators who have been wondering for many years about the legality of their operations," Schulman told NBC News.

Update for 4:50 p.m. March 7: The FAA is appealing Geraghty's decision. In a statement emailed to NBC News, the agency said it was "concerned that this decision could impact the safe operation of the national airspace system and the safety of people and property on the ground."