Nothing. In fact, the Foreign Ministry have delined it have any practical meaning and "the document no longer binds China": https://www.reuters.com/article/us-

Nothing. In fact, the Foreign Ministry have delined it have any practical meaning and "the document no longer binds China": https://www.reuters.com/article/us-hongkong-anniversary-china/china-says-sino-british-joint-declaration-on-hong-kong-no-longer-has-meaning-idUSKBN19L1J1 https://www.reuters.com/article/us-hongkong-anniversary-chin...