That is a really interesting possibility, Backwoodsman. It is being suggested that the justification for bringing it back is that Cox's advice is changed because of the Vienna Convention. Now, it is true that is not in his written advice. But it was raised in the debate and his advice on the matter sought and given. So the claim the advice has changed is on very shaky ground indeed. Also that clause of Vienna Convention concerns fundamental changes in the parties concerned. A change of Prime Minister is not such a fundamental change. A change of governing party is not such a fundamental change. A complete collapse of the finances of the UK would be, but presumably those seeking to invoke it do not think that is likely. So this a fig-leaf of an excuse, not a genuine one.

Now, if Teresa May agreed to change her red lines and adopted a more consensual approach, that would be an actual change to the deal, so it could be brought back without doubt.

Some ERG members have said they would vote for the deal on condition May resigns. That takes us into, as far as I know, other uncharted constitutional waters. There is a convention that no parliament can bind its successor, so it cannot pas a law directly restricting its successors actions. It is not clear if that applies to Prime Ministers. For example, if May agreed to adopt some of Labour's ideas, and that so-amended deal was passed with those changes to the parts of the agreement that are *not legally binding*, to what extend would a PM Boris be bound to follow them? I don't think anyone knows.