FAA Investigating Legality of Fireworks Drone Flight

Pretty much everyone on the planet has by now seen the YouTube video of a fireworks display that was shot from a drone. A report is now circulating that the FAA is investigating the legality of that flight:

According to Forbes, the FAA is now actively looking into whether drones that fly into fireworks displays is a “violation of federal regulations or airspace restrictions.”

Has anybody ever heard of such a regulation?