This has also turned into a In-Laws rant...sorryBACKGROUND:
My SIL's boyfriend got a pit bull puppy a few weeks ago. Less than a week after he got put in jail, again

and my SIL had the dog. As with everything else she does, she is making my in-laws care for the dog. My MIL is TERRIFIED of dogs, so it is only allowed in the utility room of the house. Because it started to chew on things (it is around 8 weeks old- could be teething?) from being kept up, they keep it in a cage for most of the day, apart from a couple hours in their small garden.
We went over to see them yesterday and my FIL was saying the dog was getting nippy and was constantly trying to bite my 4yo niece. I asked him what he did, and he said it wasn't really harming her so nothing. I also asked how much they were taking him for walks and he has
never been on one. My FIL said it is against the law to walk your dog without proper immunizations.
SO..
I have read all the dog laws and it seems like they can walk him as long as he has tags, which he should have if he is a pit bull (otherwise breaking some dangerous dog laws-not being registered).
I also read that at 8 weeks, they are old enough for immunizations, as they can have almost all of them at 9. My FIL said that they can't have any until they are 3-4 months old.
I found how they are treating this poor dog to be borderline abusive. Yesterday, I told them that they should start exercise and training the dog, because locking him up all day and ignoring him is going to make him be aggressive. My FIL said that you "shouldn't have to train dogs, he's just chewing on things because he is a bad breed of dog".
My husband and I begged them to take him to the RSPCA or put an ad in the paper to give him away but they won't do it because my SIL wants to keep it for when her bf gets out of jail. Based on his charges, the dog probably won't be alive when he does. Of course, SIL won't look after the dog herself, because she couldn't possibly be inconvenienced by a situation she created. We are not able to have dogs in our flat

and we don't have friends that have leases that allow dogs.
We talked about calling the RSPCA and saying that they have this dog they aren't taking care of, but we don't really feel like starting a family argument. Plus, we are applying to be foster parents, and having our nearest relatives with abuse charges on record would probably not help us.
We are going to try to sit them down and talk to them again, to try to get them to either treat the dog fairly or to give it up ASAP.
Basically, I just want to know if anyone has any further info on immunization dog laws I can give to my in laws or any advice in what to do in this situation.Sorry for the long post!