Two British men accused of killing Western hostages for ISIS are reportedly being transferred to U.S. military custody due to the incoming Turkish invasion into Syria threatening their continued detention by Kurdish forces, The Washington Post reports. Alexanda Kotey and El Shafee Elsheikh, two of the four British ISIS militants called the “Beatles” by hostages, were reportedly being held by the Kurds with the objective of making them stand trial in the U.S. Prosecutors would reportedly seek to charge the two men as “conspirators in hostage-taking resulting in death,” which carries a potential death sentence. However, prosecution of the men in the U.S. relies on whether British authorities will release evidence to American courts. The issue is currently being litigated in the Supreme Court of the United Kingdom.

Mohammed Emwazi, the third “Beatle” who is thought to have killed Americans James Foley, Steven Sotloff, and Peter Kassig, was killed in a drone strike in 2015. The fourth member, Aine Davis, was convicted in Turkey and sentenced to seven years in prison.