I am reading Commentaries on the Laws of England by Sir William Blackstone and he writes:
And by the habeas corpus act, 31 Car. II. c. 2. (that second magna carta, and stable bulwark of our liberties) it is enacted, that no subject of this realm, who is an inhabitant of England, Wales, or Berwick, shall be sent prisoner into Scotland, Ireland, Jersey, Guernsey, or places beyond the seas; (where they cannot have the benefit and protection of the common law) but that all such imprisonment’s shall be illegal;
Why is Berwick awarded special status here? I assume Berwick-upon-Tweed is meant here, is it because it's bordering Scotland?
Yes it refers to Berwick upon Tweed. it is because of Berwick's peculiar status as a "Free Burgh". Berwick was an Anglo Saxon settlement in the kingdom of Northumbria, it has been part of England then Scotland, then England again numerous times. After England last took control of Berwick it gained unusual legal status. It was north of the Tweed and yet english, so it was referred to legally as "of England, yet not a part of it". This slightly unusual legal status meant that until the wales and Berwick Act of 1746, Berwick was mentioned separately. One result of this unusual legal status is an oft quoted myth about the Crimean War. As Berwick wasn't specifically mentioned in the peace treaty, some claimed that technically Berwick upon Tweed remains at war with Russia to this day.