Who Banksy? because he has clearly given his permission in the form of a press release

So Banksy has gven his moral ascent to anyone stealing from that shop although obviously Banksy doesn’t have the legal right to do that and you will still get in trouble if the police catch you but the police in the UK don’t investigate shoplifting less than £200. Although they recently have been told to crack down on all shoplifting so that might change.