Brexit—a constitutional crisis?

There are three options in respect of Brexit. First, a soft Brexit with the UK remaining connected to the EU economic arrangements but out of the political arrangements. Second, a hard Brexit with the UK out of the economic arrangements and political arrangements but with a withdrawal agreement including a transitional period of remaining in the EU followed by a Canada-style free trade agreement. There would also have to be some arrangement that does the same job as the Irish backstop but which is acceptable to the Tories and DUP. The third option is crashing out of the EU without a withdrawal agreement, so the UK would be out the economic and political arrangements and would leave on the exit day without a transition period and then trade on WTO terms. There would be no backstop and so the Good Friday Agreement could be at risk. Alternatively, the UK could unilaterally revoke Brexit by operation of Art 50 of