Purpose: This article examines the effects and implications of the 2019 social movement in Hong Kong and those of the enactment of the National Security Law (NSL) for Hong Kong for one country two systems (OCTS). It further explores how these factors potentially promote or threaten the intrinsic value of OCTS a normative consensus. It also discusses the factors underpinning the rationale of OCTS as a normative consensus and whether this consensus is inviolable and sustainable. Design/methodology/approach: This article uses the concept of selective adaptation, especially the element of complementarity to explainthe legal behaviour of the Peopleʼs Republic of China (PRC) in relation to Hong Kong and to examine the effects and implications of the 2019 social movement in Hong Kong and those of the enactment of the NSL for Hong Kong for OCTS. It further explores how these factors potentially promote or threaten the intrinsic value of OCTS a normative consensus. It also discusses the factors underpinning the rationale of OCTS as a normative consensus and whether this consensus is inviolable and sustainable. Findings: It is still possible and feasible for China and the West to work out a normative consensus to sustain and/or restore the core values of Hong Kong – the rule of law, freedom of expression, and political participation – while accommodating the PRC's political concerns about national sovereignty and security. This intrinsic value of OCTS in terms of seeking complementarity and coexistence between the Western liberal norms of governance and Chinese socialist ideology, should be acknowledged and that the OCTS policy should remain in full force to serve as a normative consensus between China and the West, and the feasibility of this proposed normative consensus rests on the PRC's self-interest. Originality/value: This is one of the very few original research that applies the paradigm of selective adaptation to explain and understand the legal behaviour and phenomenon in relation to PRC's policy towards Hong Kong.