The Hong Kong Autonomy Act, which went into force on 14 July, provides for new powers to designate persons that are “materially contributing to, has materially contributed to, or attempts to materially contribute to the failure of the Government of China to meet its obligations under the Joint Declaration or the Basic Law” (related to the treatment of Hong Kong as a special administrative region of China). The Department of State along with Treasury have 90 days to issue a report identifying such persons.
Additionally, the Treasury has between 30 and 60 days after that to issue a report identifying “any foreign financial institution (FFI) that knowingly conducts a significant transaction with a foreign person” identified in the above report. These FFIs could become subject to US sanctions depending on the "significance" of the transactions. Text of the Act available here.
The President issued an executive order permitting sanctions against such identified persons, which is available here.
The Act also rescinds special privileges the US had granted to Hong Kong in respect of security, foreign policy and trade. US government agencies have 15 days to implement changes to treat Hong Kong like mainland China.
Over the past two weeks, the world has watched as the Chinese Communist Party smothers Hong Kong’s freedom. In 1984, China promised the United Kingdom and the Hong Kong people in front of the world that it would keep Hong Kong free and open and maintain its high degree of autonomy until the year 2047. With the draconian national security legislation that Beijing imposed on Hong Kong, which allows mainland China’s security services to operate with impunity in Hong Kong, China has broken that promise, as it has so many others... July 1 was a sad day for a territory whose autonomy and history of respect for human rights and fundamental freedoms have allowed it to flourish, but Beijing’s actions have left us with no choice.
https://www.state.gov/on-the-presidents-announcement-on-hong-kong/
