
OK , it is not common for people to be banned by the courts from keeping animals but there are a few every year although the matter is more complicated because the length of time they are banded can differ depending on the sentence.
The KC (almost automatically) stops anyone banned by the courts from having anything to do with KC activities and they would not register dogs or puppies to them.
If it is someone particular you have in mind you should be able to find the court case and the outcome on line but you will need to know the name of the person you wish to know about.
The RSPA may help but I have my doubts.