Legal barriers remain challenging obstacles in many countries to apply all available instruments in the response to HIV, TB and Hepatitis. Universal access to prevention, testing, and healthcare services is often hindered by legal obstacles or how legislation is applied in practice. This is in particular true for key populations, i.e. sex workers, drug users, gay men and other MSM, who are often discriminated against in policies and even criminalized in legislation, making their access to services limited or impossible. Besides the clear negative effect on the individual's health, these restrictive legal barriers also pose a threat on public health and increase already existing health inequalities in Europe.

People in prison and other closed settings are considered key populations by UNAIDS. According to their 2017 report “Update on HIV in prisons and other closed settings” PLHIV are overrepresented in prisons and other closed settings globally, due to criminalization of HIV nondisclosure, exposure and transmission in many jurisdictions of the world and also due to criminalization of key populations who are most affected by HIV, such as sex workers or people who use drugs, trans people and gay men and other MSM. The higher burden of HIV and other communicable diseases such as TB in prisons is also due to the overcrowding of prisons and the lack of access to HIV and co-infection prevention, treatment and care services.

Although international law recognizes the right to the highest attainable physical and mental health of every individual regardless of being deprived of their liberty, people in prison and other closed settings often suffer worse health outcomes than those in the community outside these settings.