Abstract: Respect for human rights is a defining feature of harm reduction, which is commonly characterised as a public health-based movement. The importance it attaches to ‘user-friendliness’ and the view that drug users have a right to the same respect and dignity that other users of health and social care services receive is largely undisputed among harm reductionists. Within harm reduction there is also a developing discourse identifying drug use itself as a human right; nudging harm reduction towards being a rights based movement. This allows us to describe two philosophies of harm reduction: a ‘weak rights’ version, in which people are entitled to good treatment and a ‘strong rights’ version that additionally recognises a basic right to use drugs. Prioritising human rights or public health can lead to different concepts of harm reduction and different forms of ‘right action’. Privileging health may even, in some circumstances, be consistent with prohibitionary policies if these reduce harm. By contrast, the strong rights version of harm reduction subordinates public health considerations to the right to use drugs and implies support for policies that may sometimes increase harm. In the UK, the publication of ‘The Angel Declaration’, which recognises a right to use drugs and proposes a skeletal regulatory framework for a post-prohibition era, adds to the impetus for harm reductionists to clarify whether they fully embrace a right to use drugs within their understanding of harm reduction. This paper elaborates these issues in the context of the constraints upon the development of an evidence-based approach to controlling drug use that arise from the UN Conventions of 1961, 1971 and 1988.