As the Brexit gateway opens and Britain ceases at last to be part of the European Union, there is much talk about the need for a "level playing field." This is a peculiar British phrase from the world of sports, where it means that the rules should be exactly the same for both sides so that the game is fair.

Translated into the world of governance and international negotiation it means that in working out precise arrangements for the United Kingdom's full and final departure at 11 p.m. on the night of Dec. 31 — at the end of the so-called implementation period — there should be minimum divergence by the British from the rules and regulations under which the European Union operates.

The new president of the European Commission, Ursula von der Leyen, has been quite explicit about this. In friendly but firm terms, she has stated that the less alignment there is with EU rules, regulations and directives, whether now or in the future, the more distant the partnership between the EU and the breakaway U.K. has to be, and the longer it could take to finalize a new trade deal.