In May, the Financial Times reported the Chinese government had decreed that state-owned enterprises (SOEs) could no longer hire U.S. consulting companies out of fear that those companies might pass along state secrets to the U.S. government. The potential effect on law firms, should Beijing choose to include them, is significant.

In the past decade, international firms have played a major role in guiding state-owned giants like China Petrochemical Corp., better known as Sinopec, on their multibillion-dollar overseas expansions. So such a ban could mean losing one of the most lucrative practices in China.