The opening is a bit confusing: “A Brussels plan to put a customs border in the Irish Sea if there is no Brexit agreement will be included in a divorce deal”.The idea of a No Brexit Agreement usually means No Divorce Deal, so it sounds contradictory: ie, if there’s no divorce deal we’ll have this in the divorce deal.
May is saying that if the long term free trade negotiations are “unsuccessful” then the EU wants the NI-specific backstop to take over. That would indeed involve NI staying in the customs union and single market for goods. But what does “unsuccessful” mean? Does it mean the FTA negotiations break down? Or does it mean they don’t deliver the all important guarantee that there’s no need for customs or regulatory controls on the Irish border?
May says: “I could not accept there being any circumstances or conditions in which that ‘backstop to the backstop’, which would break up the UK customs territory, could come in to force.” This is there to reassure the DUP, but it will not reassure Dublin or the EU.
But London persisted, saying the TCA has to be legally binding in the Withdrawal Agreement, and not a “vague promise” in the Political Declaration which will accompany it. But here May seems to want to have her legal cake and eat it. On the one hand she’s arguing the “backstop” has to be temporary because Article 50 demands that it’s temporary (ie, Article 50 can’t “establish a permanent relationship”).
She’s effectively throwing the EU’s own legal logic back at Brussels: the backstop (either the NI-specific one or the TCA) can’t be permanent because Article 50 is only a divorce treaty, not a future relationship treaty. And yet on the other hand London is asking Brussels to bend the rules so that the Article 50 Withdrawal Agreement *can* accommodate the UK-wide customs union, which is a future relationship issue.