I wonder how close to true the Cadfael stories are - there are a couple of mentions in them that English law did not hold in the Princedom of Wales.

Various plots arise where people escape over the boarder, visitors to Wales were reminded that their authority did not hold there, and there was one case where a Welsh family living in England was affected by the different laws of inheritance in the different countries.

I'm my own lifetime I've experienced Welsh licencing laws being rather novel, when a pub could be open on a Sunday, but not a village shop - not a problem, you take what you want to buy and leave the money in a box on the counter whilst the owner reads the paper or does some knitting and tells you the prices as you pick up the items.