National Police Board regulations and general guidelines on firearms legislation, Chapter 17
Storage of firearms and ammunition and transport of firearms
1 § According to Chapter 5, Section 1 of the Weapons Act (1996:67), anyone who possesses firearms or ammunition is obliged to take care of the property and keep it under such supervision that there is no risk of unauthorized persons gaining access to it. Supervision means that the owner has immediate control over the weapon or ammunition.
10 § In the event of a temporary brief interruption in supervision in connection with the movement of firearms on ships, the main part of the weapon or weapons equipped with 3 Swedish Anti-Theft Association (SSF) standard for padlocks and fittings class 3 or another standard that guarantees an equivalent level of protection 47 RPSFS 2009:13 weapon lock shall be stored in a locked cabin or locked vehicle parked on a locked vehicle deck. A vital part of the weapon shall be taken with you or stored at the ship's reception or with the ship's officers.
11 § In these regulations, separate storage means that the main part of the weapon, vital parts and ammunition are stored in different places. Vital parts must be kept under constant supervision. A vital part of the weapon is a part of the weapon that is necessary for the weapon to function.
Vital parts are: Rifles and shotguns with breech blocks - Breech blocks and barrels
Break-action firearms (e.g. shotguns) - Stock, breechblock and barrels. If the firearm has been fired with a blank cartridge, the fore-end or under-fittings constitute vital parts of the firearm, unless the firearm has external hammers.
Revolver - Cylinder
Pistol - Breech, barrel and barrel jacket
Therefore, according to the main rule in the Weapons Act, the owner is obliged to take care of and be responsible for their weapon.
If the passenger is travelling by car, the weapon must be stored in the car, which must be locked. A vital part must be handed in at reception, or the owner may carry it with them so that it is under their constant supervision, according to the main rule. If passengers are travelling on foot, they must keep the weapon under constant supervision and leave a vital part at reception, or alternatively take a cabin where the main part of the weapon can be stored under lock and a vital part left at reception. Weapons must, of course, always be stored in a gun bag or case during transport.
The obligation to report and notify Swedish and Finnish customs authorities when exporting and importing weapons lies with the owner of the weapon.