Statelessness and other forms of legal identity problems are a global phenomenon that affects millions of people worldwide. Those who find themselves without a recognised legal identity face daily obstructions from lack of access to a range of social, political and economic rights; with significant adverse impact on their living conditions. At a time when stateless Rohingya populations face mass expulsion from Myanmar, this paper draws attention to a less observed example of entrenched exclusion in Southeast Asia. Building upon many years of ethnographic research conducted between 2008 and 2016, the paper considers the case of ethnic Vietnamese minority populations residing on floating villages in Kampong Chhnang province, Cambodia. Members of this group are long-term residents of Cambodia, having been born and raised in the country for generations, with the exception of the period of the Khmer Rouge regime, when they were forcibly deported to Vietnam. Since their return to Cambodia in the early 1980s, individuals from this group have been regarded by Cambodian authorities as “immigrants” or “foreign residents”. Without citizenship and other documentation, these people live at the margins of society. What attempts have been made to address this problem, and how effective were these responses? This paper examines the role that law has played in the dynamic process of identity construction and social exclusion affecting this group, and how human rights and rights-based approaches to development have been used to respond to this situation. The matter has now move onto the global policy agenda with the UN General Assembly adopting, in 2015, sustainable development goals that now aspire ‘by 2030 [to] provide legal identity for all’. Hence, the use of human rights discourses and rights-based approaches can be used to mount calls for change. Yet, this paper argues that these discourses and the responses they inform may not adequately or necessarily challenge the root causes of marginalisation. At stake is not just a technocratic exercise of registering populations and making the invisible legally visible, but a highly contentious process of tackling identity politics and transforming deep-rooted social realities.