The two-year transition stage would also include British Parliament negotiating what a new trade deal between the United Kingdom and the European Union would look like. She outlined two possibilities: a close relationship, like Norway's or Switzerland's with the bloc, or a more distant one like that of Ukraine. Some commentators have pointed out that EU powers such as Germany may feel that the U.K. has to be seen to pay consequences for a Brexit, or else other EU countries may decide there's no reason not to leave themselves. A diminished trade relationship would serve as a very visible negative consequence for the United Kingdom.
As for the lawyers, the short-term benefits they might see by navigating the transition won't last, Bradford said, as many companies would eventually relocate when formerly loose trade restrictions tighten. As firms depart, so will jobs in the law.
"There's a negative consequence for the economic activity in the U.K. if there are companies moving away," she said. "If the financial activity is moving, I expect the legal business to follow that move."
Long term, she said, legal advisory work might not need to take place within London. If there's less economic activity, lawyers that currently benefit from that economic activity stand to lose eventually, Bradford said. Law firms play a critical role in mergers.
Economic activity has already dampened this year ahead of the vote. The volume of U.K. merger and acquisition deals was down 65 percent in the first half of 2016 from the same period a year earlier, according to a report from Dealogic. That compares with a global merger and acquisition decline of 27 percent.
Bradford's colleague, Columbia Law professor John Coffee, said a vote to leave is likely to further depress the number of cross-border mergers and initial public offerings of stock.
"Investment banks that depend on transactions are likely to see less mergers done in the U.K. and less IPOs done in the U.K.," Coffee said, adding that lawyers make a living off of such transactions. "If people find it easier to do an IPO on the Deutsche Boerse, then lawyers and investment bankers will go there."
The planned $30 billion merger between the London Stock Exchange and Deutsche Boerse is one notable deal that could be affected, Coffee said, as shareholders vote to approve it next month.