In reality, the decision will not stop Brexit from happening: Downing Street insisted minutes after the ruling that Article 50
-- the legal trigger for Brexit -- will still be invoked by the end of March, as planned.
Opposition parties in the houses of Parliament will try to slow down the process, tacking amendments to the legislation that is now needed. But Brexit remains on course.
However, the ruling has much more pressing political ramifications, bringing a sense of urgency to May's Friday meeting in Washington with Donald Trump.
May is the first foreign leader to meet Trump, and being "at the front of the queue" had been billed as a victory for the Prime Minister. Yet with the ink barely dry on the Supreme Court judgment, there is now greater pressure on May to make the meeting a success.
May will now be keen to strike a UK-US trade deal as quickly as possible. European leaders, including German Chancellor Angela Merkel, have given May's proposals unveiled last week for a "hard Brexit"
-- which include the UK withdrawing from the EU single market -- a frosty response.
Isolation from Europe means May needs as many friends as possible outside the EU to show that Brexit can work. For the purposes of political optics, she needs to have something to show from her meeting with the new US leader. Once Article 50 is triggered, EU rules make it difficult for the UK to forge new trade deals independent of the European bloc. The clock is ticking.
There are causes for optimism for May: With Trump withdrawing from the Trans-Pacific Partnership trade agreement
, there is definitely room for new deals to be discussed.
For Trump, the meeting is just as crucial: He also needs friends to endorse his position as he tries to reshape the new world order. Amid all the uncertainty of US protectionism and a post-Brexit UK, reassuring voters in both countries is crucial. There will be a mutual sense of wanting to make the special relationship appear even more special. Perception matters.
But how does May's keenness to strike a UK-US trade deal fit in with Trump's vision of "America First"
? The UK and US may have a special relationship, but Trump's desire to put America first is even more special to him.
On Monday evening, White House press secretary Sean Spicer hailed the UK-US special relationship but added: "We can always be closer."
This could be read two ways. In one sense, it suggests warmth from the Trump administration toward Britain, but it could also be seen as a message from the White House that there is a lot of work to do to bring May and Trump closer together. The Supreme Court has just heightened the sense of urgency on making that closeness a reality.