The National Security Law (NSL) adopted on 30 June 2020 was, in part, the product of a long-developing legal discourse regarding Hong Kong’s territorial status within the People’s Republic of China (PRC). The conceptual foundations of the NSL lie in specific propositions regarding the nature of the Central Government’s role in the governance of Hong Kong, as well as the hierarchy among relevant public law authorities, including constitutional texts and international agreements. It is important to understand these propositions, and the theoretical premises they reflect, in order to assess the NSL’s role as a major element of Hong Kong’s legal architecture extending far beyond policing and security matters per se.