Lawyers specializing in regulatory matters related to the Committee on Foreign Investment in the United States, or CFIUS, are having a busy year—especially with transactions related to Chinese investors.

On Sept. 13, President Donald Trump barred a Chinese-backed private equity firm co-founded by longtime Jones Day Beijing chief and former partner John Kao from acquiring Portland, Oregon-based Lattice Semiconductor Corp., citing potential national security threats.

Trump's decision to block Canyon Bridge Capital Partners' $1.3 billion deal was only the fourth time that a U.S. president has prohibited a Chinese investment transaction from being completed based on recommendations from CFIUS, a Treasury-led interagency committee responsible for checking foreign investment transactions for national security risks. And so far, these four transactions involving Chinese acquirers are the only ones to ever have been blocked by a presidential review.