Hong Kong
In Hong Kong, under the Firearms and Ammunition Ordinance (HK Laws. Chap 238), "an air rifle, air gun or air pistol from which any shot, bullet or missile can be discharged with a muzzle energy greater than 2 joules (1.48 ft·lbf)" are considered 'arms'. As such, a permit is required for possession (which would otherwise be illegal) and carries penalties up to a fine of $100000 . and 14 years in jail.
Read more about this topic: Air Gun Laws