Mayer Brown partner Elizabeth Espín Stern is based in Washington, D.C., not London or Brussels. But Brexit has been her business ever since Britons signed on to the idea of ditching the European Union in 2016.

The United Kingdom is set to formally withdraw by the end of the month—three and a half years after the Brexit referendum, and six years after Stern launched Mayer Brown's global mobility and migration practice in 2014.

Stern's practice has since grown from four to more than 40 lawyers, advising multinational clients on managing their international employees and navigating the legal challenges that entails, especially as countries face uncertain political and economic futures.

The departure of the U.K., the world's sixth-largest economy, from the EU, the world's second-largest economy, is one of the challenges that has been keeping Stern and her team busy.

Elizabeth Espín Stern of Mayer Brown (courtesy photo)

"Until the elections on Dec. 12 … no one knew for certain how the cliffhanger of Brexit would end," said Stern, referring to the U.K. general election that elevated Prime Minister Boris Johnson's Conservative Party to power. "Would there in fact be a hard Brexit—that after all of the start and stops with the European Union, the U.K. would abruptly leave with absolutely no plan in place?"

Stern said Johnson's December victory means that, at this point in time, the U.K.'s withdrawal from the EU is going to be a relatively organized exit, with the U.K. parliament poised to pass a withdrawal bill by Jan. 31.

With the financial sector among the industries grappling with Brexit, Stern and her colleagues have been advising financial institutions to review the locations and citizenship of their British and European workforces, and to take whatever steps that will be necessary in the coming year.

For instance, if a European national is living and working in the U.K., they might want to apply for settled status there, which would allow them and their families to stay in the U.K. after Brexit, Stern said. They have until the end of June 2021 to do so, she added.

There won't be any immediate changes between the U.K. and the EU that will directly affect workers' status, Stern noted. Until the end of the year, British and European nationals will still be able to move between the U.K. and the EU as if the former had never left the latter.

When Stern started Mayer Brown's global mobility and migration practice, she said she saw a gap in the legal market for multinational corporations in need of advice on local and regional employment rules.

"Today, there are many, many countries that require the employer to know that every employee that works for their enterprise in Country X has a lawful right to work. If the employer doesn't validate that … there is typically criminal liability for that, in most regions of the world," Stern said.

The practice group has grown to 22 partners, four counsel, 16 associates and support staff spread across four continents. Their work has become more complex, but Stern said they thrive on helping clients overcome crises and come up with "extraordinary solutions."

Stern said her international background helped position her to take on the work she handles now. She's the daughter of an Ecuadorian diplomat who advised several presidents of the small South American country and once worked for the Organization of American States.

"I feel like I returned to my roots when I launched into a global immigration practice," Stern said.