The solution proposed to this problem was, effectively, to keep Northern Ireland’s regulations in line with the EU’s and give it a special status – basically keeping it in the customs union and single market (because customs union and single markets are basically just a bunch of regulations). This was nearly agreed on Monday.
The Northern Ireland deal is the last piece of the puzzle in phase one of talks. The European Commission now believes “sufficient progress” has been made on the separation issues to move to trade talks.
This will all be far from straightforward, but the absence of further delays does mean that a Brexit deal is still possible before time runs on in March 2019 and the UK automatically leaves.
The DUP also showed that they’re calling the shots in Westminster by humiliating the Prime Minister for a week or so, and they still don’t have to agree to anything they don’t want to agree to.