Although Beijing likes to refer to HK as a “domestic” matter, international law is at the heart of HK’s constitutional order and must be considered in any attempt to implement Article 23 of HK’s Basic Law. I begin by reviewing HK’s status on the UN’s list of non-self-governing territories, which created a presumption that residents would exercise their right to self-determination upon decolonization. Although this did not occur, the Sino-British Joint Declaration can be viewed as providing a form of “internal self-determination,” a means of reconciling China’s territorial claims with HK people’s rights. I then consider how Article 23 can be implemented without violating international law. In addition to the Joint Declaration and the ICCPR, I also draw upon the jurisprudence of the ECtHR, the UN Human Rights Committee’s decisions and General Comment 34. This body of law shows it is possible to protect China’s legitimate security interests without violating HK people’s rights.