Francois Lenoir / Reuters

The U.K. High Court’s ruling Thursday that the government does not have the authority to invoke Article 50 of the Lisbon Treaty—the formal mechanism that would begin negotiations for the country’s departure from the European Unionis a blow to Prime Minister Theresa May. The ruling, which the government says it will appeal to the Supreme Court, contends that doing so without seeking parliamentary approval, which May had argued was within her power, would effectively erode parliament’s sovereignty, which is enshrined in U.K. law. In other words: U.K. lawmakers must vote on whether to invoke Article 50.

This puts the government in an awkward position. Her predecessor as prime minister, David Cameron, had staked his political future letting voters decide on the U.K.’s continued membership in the EU. And despite dire warnings about the economic and social costs of Brexit, polls remained close and tightened during the final days. Still, Cameron and others—even those championing Brexit—suspected the “Remain” side would eventually triumph in the June 23 referendum. But it wasn’t even close: 52 percent voted to leave versus 48 percent who wanted to stay. Cameron resigned as prime minister and, subsequently, as a member of Parliament. After much political jockeying, and backstabbing, among the more high-profile proponents of Brexit within Cameron’s Cabinet, May, who had tepidly supported “Remain,” emerged as the candidate to replace him. As prime minister, she said she would respect the wishes of the voters, stacked her Cabinet with prominent “Leave” campaigners, and said that she would invoke Article 50 in March 2017, thereby setting in motion an expected two-year process to negotiate the U.K.’s future relationship with the EU.

But a legal challenge, which was partially crowdfunded, on whether the government had the authority to do so complicated that plan.

The government’s position was that Parliament had, in fact, assented to the government’s authority on Article 50 when it approved the European Communities Act in 1972. That’s the law Parliament passed to allow the U.K. to join what would eventually become the EU. Not so fast, the High Court said Thursday: “[W]e decide that the government does not have power under the Crown’s prerogative to give notice pursuant to Article 50 to withdraw from the European Union.” Furthermore: “Parliament is sovereign and can make and unmake any law it chooses.”

The legal action against the government’s position was brought by Gina Miller, an investment-fund manager. Miller has said that the question in the referendum on whether to “Leave” or “Remain” in the EU was “far too binary.” She was, she told Business Insider, for “remain, reform, and review.” She argued that if Article 50 were invoked without the proper steps, it would weaken the U.K.’s negotiating position during Brexit talks with other EU nations. But perhaps more pertinent was her argument that the government's invocation of Article 50, without Parliament's buy-in, would set a dangerous precedent.

“We must remember that the U.K. doesn’t have a written constitution—it is made up of precedent,” she told Business Insider. “If we set the precedent that a government can use their royal prerogative to take away people’s human rights, that is taking us into a very dangerous political environment.”

What does all this mean for Brexit? If the U.K. government wins its appeal at the Supreme Court, it will mean the government does have the authority to invoke Article 50, presumably next March. But even if it doesn’t, and lawmakers indeed do get a say in the matter, it’s highly unlikely they will undo the decision of a majority of voters—no matter what the U.K.’s elites think of Brexit.

Still, the court’s decision is likely to heighten the political and economic uncertainty triggered by the Brexit vote. Although some of the most dire warnings about the impact of a vote for Brexit have yet to materialize, the costs have already been high for the U.K. economy and its currency, mostly because it’s unclear what shape the U.K.’s future relationship with the EU will take. While some Brexit proponents had argued that the U.K. would continue to have free trade with the bloc after it leaves, EU officials have dismissed that idea unless the U.K. allows the free movement of EU citizens—a highly unlikely proposition given that many Brexiters listed immigration from the EU as their primary reason for voting “Leave.” Nor is the EU’s ability to forge the sort of agreement that will satisfy all sides assured. As it showed during recent trade negotiations with Canada—which nearly failed due to the objections of a single region in Belgiumthe EU is not a monolithic entity. Free trade, while popular in the 1990s when the bloc was born, is now facing a backlash globally, and imposing political costs on many of its most ardent supporters. So while the High Court’s ruling was a major twist in the Brexit saga, in one respect the court has left the situation much the same as it was before: The U.K.’s future remains very unclear.

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