Or, Ms May may not and must not; at least, not yet.
(For readers outside of the (ice) hockey world, substitute “end of first half”.)
The UK QB ruled unanimously (3-0) this fine English morning that the Tory gov’t cannot use the Crown’s prerogative to initiate the UK’s withdrawal from the EU. The decision to withdraw or not – the decision whether to give notice under the applicable EU treaty – is for Parliament to make, not the party in power in Parliament; aka the “gov’t” or the Crown.
 for the reasons we have set out, we hold the Secretary of State does not have power under the Crown’s prerogative to give notice pursuant to Article 50 of the TEU for the United Kingdom to withdraw from the European Union.
R (Miller) v Secretary of State for Exiting the European Union 2016 EWHC 2768 (Admin)
A spokesperson from the Crown – or UK gov’t – or the Tory party, pick your poison, announced, as one might expect, that the decision will be appealed.
In a “I’m not sure how it’s related but he’ll eventually grope towards an explanation development”, Donald Trump’s campaign has announced that he blames “this interference by unelected, wig wearing, black dress wearing elites with the will of the true representatives of the pure wool people in the United Kingdom on ‘Crooked Hillary.’ (satire).
Disclosure: a speaker, yesterday, at a lecture I attended used the Henry 2 v Henry 8 line to describe the possible results, saying that, of course, the decision wouldn’t be put quite that way. As much as I’d love to be able to claim it, it’s not my concoction.