Gun laws in Belgium are strict but well thought out.
First, to own and buy a weapon, you must be a recognized hunter or hobby/sport shooter.
So you need to have a hunters permit or have passed an exam as sport shooter before you can purchase your own weapon.
Note that permissable weapons are devided in four categories: carbines, pistoles and revolvers, dubbleshot shotguns and blackpowder weapons (automatic rifles and combat shotguns are also banned for civilian use). You need to do an exam for every category of weapon you plan to own and or use (so just because you have a permit for a carbine does not mean you can buy a dubbleshot).
Once you have a permit, you can buy as many weapons as you like, but every gun must be registered after purchase with the police. Furthermore, there are permit renewals every 5 years (which is usually just a formality) and there are laws considering how to store weapons at home and what kind of storage capacity and safety measures are required depending on the amount of weapons you have.
That's Belgium's gun law in a nutshell.