Since its founding in 1954, high-energy physics laboratory CERN has been a flagship for international scientific collaboration. That commitment has been under strain since the Russian invasion of Ukraine in 2022. CERN decided to cut ties with Moscow late last year over deaths resulting from the country's "unlawful use of force" in the ongoing conflict.

With the existing international cooperation agreements now lapsing, the Geneva-based organization is expected to expel hundreds of scientists on November 30 affiliated with Russian institutions, Nature reports. However, CERN will maintain its links with the Joint Institute for Nuclear Research, an intergovernmental center near Moscow.

CERN was founded in the wake of World War II as a place dedicated to the peaceful pursuit of science. The organization currently has 24 member states and in 2019 alone hosted about 12,400 users from institutions in more than 70 countries. Russia has never been a full member of CERN, but collaborations first began in 1955, with hundreds of Russia-affiliated scientists contributing to experiments in the ensuing decades. Now, that 60-year history of collaboration, and Russia's long-standing observer status, is ending. As World Nuclear News reported earlier this year:

The decision to end the cooperation agreement was taken in December 2023 when CERN's Council passed a resolution "to terminate the International Cooperation Agreement between CERN and the Russian Federation, together with all related protocols and addenda, with effect from 30 November 2024; To terminate ... all other agreements and experiment memoranda of understanding allowing the participation of the Russian Federation and its national institutes in the CERN scientific programme, with effect from 30 November 2024; AFFIRMS That these measures concern the relationship between CERN and Russian and Belarusian institutes and do not affect the relationship with scientists of Russian nationality affiliated with other institutes." The cooperation agreement with Belarus will come to an end on 27 June, before the Russian one ends.

It's not yet clear how this decision will impact scientific research at CERN. Russia's 4.5 percent contribution to the combined budget for ongoing experiments at the Large Hadron Collider has already been covered by other collaboration members. Some think the effects will be minimal, since researchers have had plenty of time to prepare for the exit. Certain essential staff members have successfully found employment outside of Russia so that they can stay on.

Others are less confident. “It will leave a hole. I think it’s an illusion to believe one can cover that very simply by other scientists,” particle physicist and CMS member Hannes Jung of the German Electron Synchrotron in Hamburg told Nature. He's also a member of the Science4Peace Forum, which opposes restrictions on scientific cooperation.

Jung supports CERN's decision to continue working with JINR. “I have the feeling it marked a bit of a change in the way things are handled," he said. But not everyone is happy about that decision. Boris Grynyov, director of the Institute for Scintillation Materials in Kharkiv, Ukraine, told Nature that the decision was "a big mistake."