President Trump's war on illegal immigrants is expanding to the millions who come here legally for a brief job or to attend college, then illegally overstay their visas.

New guidance from the State Department based on a Trump executive order calls for a crackdown on immigrants who don't return home as promised and it urges U.S. diplomats in foreign posts to look skeptically at new visa applicants.

The move is being heralded by groups pushing the administration to enforce immigration laws and tackle the huge number of visa "overstayers" in the United States.

The Department of Homeland Security just reported that there are 739,000 immigrants who have overstayed their worker, student, and other visas. Of those, nearly 80,000 were foreign students supposed to leave in 2016 but apparently did not, making them a significant contribution to the illegal immigration problem.

Jessica M. Vaughan, the director of policy studies for the Center for Immigration Studies, told Secrets that the order will have a huge impact because foreign students notoriously stay too long, often then taking U.S. jobs.

What's more, student visas are the favorite of terrorists, she said. "Foreign students have one of the highest rates of overstaying visas of any category – much higher even than tourist visas. It's one of the favorite visas for terrorists to try to obtain, because it offers a longer duration of stay. Some of the 9/11 terrorists were given student visas," she said.

Vaughan added, "Too many people enroll in U.S. colleges just to get a foothold in the United States rather than to pursue an education, and for too long the State Department has looked the other way, preferring instead to promote U.S. colleges. The higher education industry also lobbies Congress and the State Department relentlessly for help in attracting foreign students and cries foul when it thinks the law is being enforced too much, because many of these schools view foreign students as a cash cow, and don't care if they stay over to compete for jobs with U.S. students."

The new guidance, detailed in a report from the National Law Review, requires applicants to convince U.S. visa officials that they will return home after their visa expires. "The revisions appear to instruct officers to apply a more rigorous -- and, arguably, protectionist -- approach to determining whether an applicant meets the requirements of the visa category in question," said the report.

Vaughan said the impact will be important in cracking down on future illegals.

"For years, consular officers have been instructed to review foreign student applications with a wink and a nod even when it is obvious that the student never intends to go home," she told us.

"This is at odds with the traditional view that the U.S. should encourage foreign students to come and then return home to use their education to the benefit them and their home country, and to spread a positive view of America across the world. The Trump approach will pay dividends in the future for our relations with other countries and also help end abuse of the student visas as a stepping stone to permanent stays here," she added.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com