Global lawyers and companies in Hong Kong are unsure about the city’s future as a global business hub following Beijing’s introduction of a new national security law for the city and the tough U.S. sanctions that are expected to follow.

Tuesday’s passing of the new law marked the most significant shakeup to Hong Kong’s constitution since the city’s return to Chinese rule in 1997. With local authorities already strictly enforcing the law just hours after its full text was made public, global law firms are scrambling to deal with clients’ inquiries about how the new law will affect their bottom lines—an increasingly complicated question as the United States ramps up its response.