In the UK, unless you own a Fire Arms Certificate, the power limit for Air Rifles is 12 foot pounds force (ft-lbf). This is about 16 joules of energy. For Air Pistols the power limit is 6 ft-lbf or about 8 joules. You are allowed spring guns, CO2 guns, and pump up guns, but after a change to the law in the early 2000s, you are not allowed air cartridge guns. I had 2 of those (worth about £700) confiscated by the police, with no compensation. One day I am enjoying my hobby and the next I'm breaking the law. And all because a few idiots had modified the guns (revolvers and Beretta clones ) to take .22 amunition.
I still have 2 Webley spring powered pistols and a Park RH93 .22 air rifle that uses 2 opposing spring powered pistons that stop any vibration on firing.
I also have a custom bow, but you cannot use archery for hunting in the UK.
"Be yourself, everyone else is already taken." - Oscar Wilde