Europe’s particle-physics laboratory CERN will expel hundreds of scientists who are affiliated with Russian institutions on 30 November unless they move to establishments outside of the nation. The date marks the official end of the lab’s collaboration with the Russian Federation, following CERN’s decision to cut ties with the country after its 2022 invasion of Ukraine.

But tension over CERN’s relationship with Russia remains among researchers, because the organization will continue to work with Russia-based scientists through an agreement with the Joint Institute for Nuclear Research (JINR), an intergovernmental centre in Dubna, near Moscow. JINR’s arrangement with CERN is separate from Russia’s. The decision to not cut ties with the lab has divided researchers, some of whom point to its relationship with the Russian state, which continues its deadly war in Ukraine.