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.