Are you living in the UK, Liam?
If so, from the......."The Dangerous Dogs Act 1991"
...."The following dogs, and also
cross-bred pit-bulls, are dangerous dogs under the meaning of the Act:
1. Pit Bull Terrier
2. Japanese Tosa
3. Dogo Argentino
4. Fila Braziliero
It is illegal to possess such a dog without a certificate of exemption, which is granted once the dog is neutered, insured, and has a transponder implant. These dogs cannot be "in a public place without being muzzled and ... being securely kept on a lead by a person who is not less than 16 years old."
More detail on this site....
Hope this helps.