This memorandum analyses the constitutionality of the federal government’s requirement that international relief organisations adopt policies explicitly opposing prostitution and sex trafficking if they wish to participate in federally-funded programmes designed to combat the worldwide spread of HIV/AIDS. We conclude that the First Amendment bars Congress from requiring relief organisations based in the United States to adopt a specific policy position opposing prostitution as a condition of participating in federally-funded programmes delivering HIV/AIDS prevention, treatment and related social services.