Published data show that new HIV prevention strategies including treatment-as-prevention and pre-exposure prophylaxis (PrEP) using oral antiretroviral drugs (ARVs) are highly, but not completely, effective if regimens are taken as directed. Consequently, their implementation may challenge norms around HIV prevention. Specific concerns include the potential for ARV-based prevention to reframe responsibility, erode beneficial sexual norms and waste resources. This paper explores what rights claims uninfected people can make for access to ARVs for prevention, and whether moral claims justify the provision of ARV therapy to those who do not yet clinically require treatment as a way of reducing HIV transmission risk. An ethical analysis was conducted of the two strategies, PrEP and treatment-as-prevention, using a public health stewardship model developed by the Nuffield Bioethics Council to consider and compare the application of PrEP and treatment-as-prevention strategies. We found that treating the person with HIV rather than the uninfected person offers advantages in settings where there are limited opportunities to access care. A treatment-as-prevention strategy that places all the emphasis upon the positive person's adherence however carries a disproportionate burden of responsibility. PrEP remains an important option for receptive partners who face increased biological vulnerability. We conclude that the use of ARV for prevention is ethically justified, despite imperfect global to drugs for those in clinical need. The determination of which ARV-based HIV prevention strategy is ethically preferable is complex and must take into account both public health and interpersonal considerations.