International students who are pursuing degrees in the United States will have to leave the country or risk deportation if their universities switch to online-only courses, Immigration and Customs Enforcement announced Monday.

The move may affect thousands of foreign students who come to the United States to attend universities or participate in training programs, as well as non-academic or vocational studies.

Universities nationwide are beginning to make the decision to transition to online courses as a result of the coronavirus pandemic. At Harvard, for example, all course instruction will be delivered online, including for students living on campus. For international students, that opens the door to them having to leave the US.