Blasting a drone out of the sky may, or may not be legal, but is highly likely to lead to a court appearance.
For government agencies there is a less destructive (but apparently no less effective) counter-measure available:
http://the-gadgeteer.com/2015/10/28/new-defense-against-drones-is-available-but-only-for-law-enforcement-and-the-government/
http://www.battelle.org/our-work/national-security/tactical-systems/battelle-dronedefender / new defense against drones law enforcement office police LEO military security government drones drone quadcopters popular fun to fly people misuse fly flying sensitive airspace security privacy hunting them down firearm guns blazing government law enforcement Battelle Drone Defender drone defender defensive weapon directed-energy directed energy weapon UAS unmanned aircraft systems countermeasure remote control drone disruption GPS disruption seize remote controls drone land safely without damage averting any threat performed consistently well in field trials Battelle website DroneDefender cold start time continuously operate for five hours effective diameter cone of 30° point and shoot Battelle website device authorization authorize authorization FCC Federal Communications Commission approval obtained fun drones fly Battelle website Battelle science technology solve solving major technology center centre national laboratories Battelle research and development R&D designs manufactures delivers critical services government commercial customers national security sciences /
