Austria - No restrictions in fpe but limit on caliber (FAC req for .25 and above)
Australia - FAC required for everything and anything.
Belgium - No restrictions on rifles, pistols max 7.5J
Bulgaria - No restrictions
Canada - 500 fps limit without a PAL
Cyprus - .177 only (No information on energy levels at this time)
Czech republic - 12 fpe (16 Joules)
Denmark - No restrictions, but soon will have restrictions imposed due a change in the legislation.
Estonia - No limits in .177
Finland - No restrictions* (Require confirmation) Possible restrictions to be implemented for higher fpe
France - 7.5 fpe (10 Joules)
Germany - 6 fpe (7.5 Joules)
Greece - No power or Calibre restriction, Silencers and Scopes are banned by law. Hunting is not allowed.
Holland - No restrictions
Hungary - 6 fpe (7.5 Joules)
Italy - 6 fpe (7.5 Joules) must be over 18 to buy, over 10 to shoot it with presence of a parent; >6 fpe you need a f.a.c. and you've to declare the purchase to the police. NO Hunting.
Latvia - 12 Joules
Lithuania - 7.5 Joules (NO hunting allowed)
Luxembourg - FAC required for everything and anything.
Malta - FAC required for everything and anything. (Thanks Air-Tech)
New Zealand - Currently no restrictions except that you must be over 18 if you do not have a FAL ( firearms licence) a 25fpe (34 Joules) limit has been proposed for unlicenced users though, but not yet in law
Northen Ireland & EIRE - Airguns or CO2 guns that are in excess of one (1) Joule (0.737 ft/lbf) require to be held on an FAC.
Norway - No restrictions
Poland - 12.5 fpe (17 Joules) (NO hunting allowed) >17 Joules allowed if gun is registered with police (Formality)
Portugal - .177 or .22 Max velocity of 1181 fps Hunting not allowed
Romania - ?
Russia - 6 fpe (7.5 Joules) (Unsure of this one)
Slovak republic - 11 fpe (15 Joules)
Slovenia - ?
South Africa - Below .22 No restrictions. .22 and above - Max 7.5J No 'hunting'* with airguns, but pest control allowed, no shooting in built up areas.
Switzerland - ?
Spain - 18 fpe (24.5 Joules)
Sweden - 7.5 fpe (10 Joules (same for rifles and pistols) semi- or full auto airguns: 3 Joules.)
Turkey - No restrictions
UK - 12 fpe (16 Joules)
USA - No restrictions (Except New Jersey, Delaware, Massachusetts and Michigan) Also numerous restrictions when within City Limits, varies state to state