The Department of Homeland Security announced a new policy to cap the duration of international students’ visas to four years, cracking down on those who overstay their time in the United States.

The rule change overrides a 1978 policy, known as duration of status, that allowed foreign students to stay in the U.S. as long as their studies required, without having to interact with immigration officers. With its new visa rule, the Trump administration closed the loophole by setting a fixed time frame for such students.