Airsoft weapons are legally equated with air rifles. The age limit for buying an airsoft weapon is therefore 18 years in Sweden. To possess an airsoft weapon, the age limit is 18 years.  The use of weapons under the age of 18 requires that an adult supervises the whole thing. It is not allowed to lend an airsoft weapon if it can be assumed that the borrower will abuse the weapon.
In Chapter 2. 1 § 2 paragraph of the swedish Weapons Ordinance ( 1996:67 ) one can read that:
" A permit is not required for the 18-year-old if the weapon has a limited effect in relation to other comparable firearms (power-restricted weapons) and the weapon is1. a carbondioxide, air or spring weapon or a weapon with another similar ejection agent and is intended for target shooting, or 2. a harpoon weapon. "
As for the limited effect, chapter 1 can be found. Section 2 Of the swedish Weapons Ordinance ( 1996:70 ) read:
' A carbondioxide, air or spring weapon shall be considered to have the limited power referred to in Chapter 2. Section 1 of the Firearms Act ( 1996:67 ) if a projectile from the weapon four meters from the mouth of the barrel has an impact energy of less than 10 joules. A fully or semi-automatic carbondioxide, air or spring weapon shall be considered to have such a limited effect if a projectile from the weapon four metres from the mouth of the barrel has an impact energy of less than 3 joules.