The need for customs arrangements will arise independent of whether or not an agreement with the EU will be struck or how such an agreement will look like, but the aim is
still some kind of free trade agreement, with fishing rights and a level playing field (mostly related to state aid in the post-Brexit UK) being the critical issues (both also spelled out in the political declaration, signed by both UK and EU, though it seems
only the EU actually read the text, see below). While the opposition against the ECJ and other European institutions having too much control over the UK is understandable (given the lack of British representation), there is little trust left in Brussels in
assurances by the UK government to not undermine the level playing field, given experiences over the past year. One recent example is the letter by Mark Francois (head of European Research Group) to Michel Barnier pointing to the desire for complete sovereignty
completely, which ignores the special position of Northern Ireland (with EU institutions continuing to have an important role) in the legally binding Withdrawal Agreement and the aspirations for a level playing field (implying a role for the ECJ in interpreting
EU law) signed by both UK and EU in the Political Declarations. It seems the ERG did not quite do their research before voting for WA and PD.