the scottish airgun license bodies take on it http://airweapon.scot/faqs/

What guns are not covered by the new law?
The new law does not distinguish between different firing mechanisms – if your air weapon has a barrel and can fire a missile between 1 joule and 12 foot pounds (or 6 foot pounds for an air pistol), then it is covered by the new legislation.

The law does not cover guns that are essentially toys, or which are not considered firearms. For example, BB guns or airsoft guns will not usually require a certificate. If in doubt, ask your firearms dealer or the police.

Crossbows and underwater guns, such as those used for spear-fishing, are also not covered by the new legislation.


Are airsoft guns covered?
Realistic imitation airsoft guns with a muzzle energy below 2.5 joules (or 1.3 for fully automatic guns) are not covered by the new legislation. These guns are already controlled by the Violent Crime Reduction Act 2006. Airsoft guns above these muzzle energies may require a certificate – you should contact the police for advice.