The Trump administration has given final notice on plans to implement stricter rules for foreign students, including a ban on staying in the United States for more than four years unless they obtain permission from the federal government.

The ability to change programs and transfer between universities and colleges will also be restricted. Until now, higher education institutions had the power to grant visa extensions.

The policy, which goes into effect in September, “combats rampant visa abuse and strengthens national security through regular investigations,” the Department of Homeland Security said.

The Association of International Educators described the new rules as “misguided and unnecessary.”

Until now, foreign students with F-1 visas and J-1 exchange visas were admitted to the United States under “duration of status,” which meant they could stay in the country for the time necessary to finish their studies. The new rules will put a time limit on that stay.

Secretary of Homeland Security Markwayne Mullin said: “For decades, foreign students have been admitted to the United States indefinitely, allowing thousands of people to abuse our immigration system by perpetually enrolling in courses to avoid having to leave the United States.”

While most U.S. undergraduate programs typically last four years, graduate programs, such as doctorates, typically take longer to complete.

Most international students are enrolled in postgraduate courses, especially those in the fields of science and technology.

These courses typically require more time to complete and publish research. Lack of research funding and personal circumstances can also often lengthen the study period.

Under the new rules, foreign students will now also have 30 days to pack up and leave after graduating or switch to a different visa category, compared to the previous 60-day grace period.

NAFSA: The Association of International Educators, a nonprofit that advises schools on enrolling foreign students, criticized the new rules.

Its chief executive, Fanta Aw, said the new policy “injects uncertainty, bureaucracy and fear into a system that has worked effectively for a long time. It is a solution in search of a problem.”

The new rules are part of a broader approach by the Trump administration to reduce the number of foreign students and restrict immigration to the United States.

The administration has tried to limit the number of foreign students at some elite universities and has taken steps to revoke the visas of students who have been critical of American foreign policy.