HONG KONG—Global banks and other financial institutions in Hong Kong are scrambling to find out details of China’s planned imposition of an anti-sanctions law on the city, and trying to understand how it could impact their operations in the financial hub. Beijing adopted a law in June under which individuals or entities involved in making or implementing discriminatory measures against Chinese citizens or entities could be put on an anti-sanctions list of the Chinese regime. Financial firms are closely watching a meeting this week of the National People’s Congress Standing Committee, the highest organ of China’s rubber-stamp legislature, for signs on how and when similar legislation will be introduced in Hong Kong. Hong Kong leader Carrie Lam said on Tuesday she did not have an explicit timetable for its implementation. The move came as the U.S. government imposed several rounds of sanctions on Hong Kong and Chinese officials over Beijing’s …