If you're decent in the country where I live, you're allowed to own one thing or another, but not fully automatic things.
But you're not allowed to wear it on the street, and if you use it at home to protect yourself against burglars, you'll lose everything and go to jail.As for self-defense, it's almost impossible to fight for in court, every judge will tell you "how did you know he wanted to kill you?" in short, the burglar has to shoot you first before you can shoot him.
Even if you end up being in the right, which is rare, your weapons will be confiscated and you will have an entry in your papers about it and as long as this entry is in your papers, you will no longer be able to buy weapons.
You can also have one or two more serious traffic offenses such as driving 30 miles over the speed limit, and the police can then confiscate all your weapons.
Still questions?