11 June 2018 Alasdair Smith is an Emeritus Professor of Economics and Dr Peter Holmes is Reader in Economics at the University of Sussex. They are both Fellows of the UK Trade Policy Observatory. On June 7, after prolonged internal discussion, the UK government published its paper proposing the extension to the whole UK of the ‘backstop’ provision in the EU draft withdrawal agreement to incorporate Northern Ireland (NI) into the EU’s customs territory until another solution can be found for the problem of the Irish border. The UK is unenthusiastic about the backstop and hopes it will not be needed, but wants any backstop to cover the whole UK, so as to avoid the need for border inspections of trade between NI and the rest of the UK (GB). Perhaps surprisingly, the government paper does not address the fact that the EU’s proposal is for NI to be included in a ‘common regulatory area’ as well as in a de facto customs union: any backstop needs to deal with regulation as well as customs. […]