There are no state lines in the UK, and even the different countries within have no restrictions - few slightly different laws, but nothing to stop you buying beer anywhere you want, and taking it anywhere you want.
Even more so in the EU, my daughter who lives in the Netherlands commonly goes to Germany to fetch beer (or at least she did until she was diagnosed at gluten intolerant). But she lives near the German border, so it's only like driving down to the local shop.
In fact where she loved before, when she worked at Chemelot, she used to walk to Germany to fetch beer