The park service is referring to small "Unmanned Aerial Vehicles," like the DJI Phantom. Officials say, in recent years, the park has experienced an increase in visitors using drones inside the park to film climbers and views above the treetops in the national park.
An uptick in this kind activity isn't surprising. Recently, the price and accessibility of small, "personal" drone aircraft has come way down. Amateurs and hobbyists can outfit the devices with small cameras, such as GoPros, getting high definition aerial photographs for around $1,000.
"Drones can be extremely noisy," wrote the Park Service, "and can impact the natural soundscape."
The service referred to a section of the Code of Federal Regulations, 36 CFR 2.17, which reads, “delivering or retrieving a person or object by parachute, helicopter, or other airborne means, except in emergencies involving public safety or serious property loss, or pursuant to the terms and conditions of a permit” is illegal.
The law exempts "official business of the Federal government" and emergency rescues. Indeed, actual military drones have been deployed to help with fire fighting as recently as last year.
Despite the passage in the CFR the service cites, federal law has been particularly unclear on the use of drones by citizens. The Federal Aviation Administration has not yet drafted full regulations for the domestic use of drones and is not expected to until the fall of 2015. And this year, a federal judge ruled that the FAA doesn't even have the authority regulate hobbist aircraft.
While the regulation works out, enjoy some of the great shots drone have taken of America's most iconic national park.