Fifteen years have passed since the shelving of the National Security (Legislative Provisions) Bill by the HK government after mass protests. There have been no indications of when new legislative proposals might be introduced or the possible shape of such proposals. It is argued that, while the 2003 bill can serve as a starting point for thinking about a new law, important developments in Hong Kong, Macau, and Mainland laws also need to be considered. I propose a set of legislative guidelines based on the human rights and criminal law jurisprudence of HK’s highest court and identify relevant aspects of the Macau and Mainland national security laws that should be taken into account. The anti-terrorism law experience of other countries is also relevant as guidance on whether the proscription mechanism of 2003 should be reintroduced. Finally, the delineation of a proposed offence of secession is discussed in the context of recent debates on HK independence.