A lawsuit seeking to force Prime Minister Theresa May to consult parliament before beginning Britain’s exit from the European Union will be taken “very seriously” and may reach the Supreme Court by December, Judge Brian Leveson said.

“The court takes this litigation very seriously and will move expeditiously,” Leveson said during a hearing Tuesday. The case is “of such constitutional importance it is difficult to see why” it won’t move quickly to the Supreme Court after a two-day hearing that starts Oct. 15.

The lawsuit seeks to force the prime minister to obtain an Act of Parliament before initiating Britain’s exit from the E.U. by invoking Article 50 of the Lisbon Treaty. Oliver Letwin, the minister overseeing the task force preparing for the exit negotiations before May appointed David Davis to head a new Brexit department, said it’s the prime minister’s responsibility to trigger article 50, citing advice from government lawyers.

Gina Miller, who Leveson called a “concerned citizen,” will be the lead claimant. Hairdresser Deir Dos Santos, a group of unnamed U.K. citizens living in France and other expatriates, will also be party to the proceedings, he said. The government, which has yet to provide a detailed response to the lawsuit, must file its defense by Sept. 2, Leveson said.

May has pledged to respect the will of the people and carry out Brexit, having advocated remaining in the EU before the June 23 vote.

The current position is “notification will not occur before the end of 2016,” Jason Coppel, a lawyer representing the government, said during the hearing.

The government’s willingness to wait before invoking Article 50 is “welcome news for businesses,” said Ros Kellaway, a lawyer at law firm Eversheds in London.

“Businesses could be forgiven for being fearful of protracted Article 50 negotiations, but the reality is, a longer wait to get things right will be very much in their best interests,” said Kellaway, who is head of the firm’s competition and regulatory unit. “Especially so given the staggeringly complex and multi-faceted nature of Brexit.”

Topics Lawsuits Europe