Of course there is no need of parliamentary approval before invoking Article 50.
But only Parliament can repeal the European Communities Act, and only Parliament can enact the domestic legislation without which any deal to withdraw would be a dead letter.
For example, the agreement to pay the EU to pretend that the City of London still mattered tuppence, so to speak. Bless.
But there may never be any such deal, just as there may never be any attempt to repeal the European Communities Act.
What there will certainly be, however, is the most Eurofederalist measure ever proposed in any country, the hilariously misnamed Great Repeal Bill.
That Bill will in fact declare every EU law to be that of the United Kingdom even after we had left. But, being a Bill, it is susceptible of amendment.
Five ought to be proposed, to come into effect regardless of whether or not, as becomes less likely by the day, we ever actually withdrew from the European Union.
First, restoring the supremacy of United Kingdom over European Union law, using that provision to repatriate industrial and regional policy as Labour has advocated for some time, using it to repatriate agricultural policy, and using it to restore the United Kingdom's historic fishing rights of 200 miles or to the median line.
Secondly, requiring that all EU legislation, in order to have any effect in this country, be enacted by both Houses of Parliament as if it had originated in one or the other of them.
Thirdly, requiring that British Ministers adopt the show-stopping Empty Chair Policy until such time as the Council of Ministers meets in public and publishes an Official Report akin to Hansard.
Fourthly, disapplying in the United Kingdom any ruling of the European Court of Justice or of the European Court of Human Rights unless confirmed by a resolution of the House of Commons, the High Court of Parliament.
And fifthly, disapplying in the United Kingdom anything passed by the European Parliament but not by the majority of those MEPs who had been certified as politically acceptable by one or more seat-taking members of the House of Commons.
These would all do as one long amendment, if possible.
Jeremy Corbyn, over to you.