Staying in a customs union after Brexit won’t resolve the Irish border issue

The EU is unlikely to accept a request from the UK that it should have a say over the EU’s trade agreements. Article 207 of the Lisbon treaty makes clear that the common commercial policy is exclusive to the EU’s direction. Turkey, which is in a partial customs union with the EU, has to follow EU trade agreements with third countries but has no say on them. The reality is that in a customs union all the power would rest with the EU, with the UK as a follower.