Although the law prevents the country from backing out without due notice, Russia has not shown much regard for international law recently.
Given this, Mr Chen said it would cause significant blowback for a country that is already suffering financially, and it wouldn’t necessarily affect the obligations of other nations.
He said: “That would severely undermine trust in and prospects of Russian cooperation in the future.
“Technically, any country, including the UK, can withdraw (as cooperation of the UK under the ESA is not affected by Brexit), and it would not affect the rights and obligations of other existing partners to the ISS IGA.”
Article source: https://www.express.co.uk/news/science/1588916/Russia-vs-Ukraine-ISS-space-evg