Baumgärtel’s research concerns the human rights of vulnerable migrants such as refugees, asylum seekers and undocumented migrants. As a senior researcher of the NWO research project “Cities of Refuge” (2017-2022), he focused on the international legal obligations and policy initiatives of cities and local governments in the reception and integration of refugees. He also has a broader interest in issues of social justice and their connection to human rights, both as legal guarantees and as normative aspirations. He was a Petar Beron Research Fellow (2024-2025) at South-West University “Neofit Rilski”, where he conducted a project financed by the Bulgarian National Science Fund on the exclusion of vulnerable migrants from the protection system of the European Convention on Human Rights.