Protestors rally against the immigration ban at New York's JFK airport. (Thomas Johnson/The Washington Post)

Thousands of leading academics, alarmed by an executive order signed by President Trump last week instituting “extreme vetting” of refugees with a goal of keeping terrorists from entering the country, have signed onto a petition denouncing his action.

The executive order began a temporary ban on allowing people from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen from entering the United States. It also suspended the U.S. Refugee Admissions Program for 120 days.

“I’m establishing a new vetting measure to keep radical Islamic terrorists out of the United States of America,” Trump said when he signed it. “We don’t want them here. We want to make sure we are not admitting into our country the very threats our soldiers are fighting overseas.”

Some welcomed what they saw as a strong signal that the United States would work to exclude people intent on doing harm.

But on college campuses across the country in recent days, many people reacted to the Trump administration’s actions with alarm and protests, such as a rally at Harvard University on Jan. 27.

The online petition grew rapidly from its start Thursday evening. An organizer of the effort said Jan. 27 that they were getting about 10 emails a minute and that 15 to 20 volunteers were working to add signatures.

By early Monday, the list had grown to 40 Nobel laureates. By Friday more than 20,000 verified U.S. faculty members had signed. One hundred and four of the signatories were winners of prestigious academic awards such as the Fields, Turing, Dirac, Clark and Poincare medals, the Pulitzer and Breakthrough prizes, and the MacArthur Fellowship. Signers included 572 members of the National Academies of Sciences, Engineering, and Medicine.

What’s at stake, said Emery Berger, a professor in the College of Information and Computer Sciences at the University of Massachusetts Amherst, begins with free exchange of information. Berger is not one of the organizers of the petition but supports the effort.

Berger said he has already heard academics overseas planning to avoid, or boycott, conferences in the United States. “It’s very chilling,” he said.

And, he said, students are horrified at the prospect of not being able to get back to their U.S. university if they return to their home country.

“I’m sure it will send really promising star students across the border to Canada or elsewhere,” Berger said. The order comes just as many U.S. universities are offering admission to overseas students for the next academic year. He said an administrator told him Friday to get admissions offers to top Iranian students “yesterday.”

Trump has repeatedly called for more stringent limitations on immigration to the United States, especially after a terrorist attack in December 2015 in San Bernardino, Calif. In that attack, an American-born man and his Pakistani wife, who entered the United States on a K1 (fiancee) visa, gunned down 14 people during a holiday work party.

After an attack at Ohio State University in November, Trump tweeted that “ISIS is taking credit for the terrible stabbing” and that Abdul Razak Ali Artan, the Ohio State student and legal permanent resident who drove a Honda sedan through a crowd outside a school building before slashing at people with a butcher knife, was “a Somali refugee who should not have been in our country.”

The petition against Trump’s order, with its growing list of academics, reads, in part:

This Executive Order is discriminatory. The EO unfairly targets a large group of immigrants and non-immigrants on the basis of their countries of origin, all of which are nations with a majority Muslim population. This is a major step towards implementing the stringent racial and religious profiling promised on the campaign trail. The United States is a democratic nation, and ethnic and religious profiling are in stark contrast to the values and principles we hold.

This Executive Order is detrimental to the national interests of the United States. The EO significantly damages American leadership in higher education and research. … From Iran alone, more than 3,000 students have received PhDs from American universities in the past 3 years. The proposed EO limits collaborations with researchers from these nations by restricting entry of these researchers to the U.S. and can potentially lead to departure of many talented individuals who are current and future researchers and entrepreneurs in the U.S. We strongly believe the immediate and long term consequences of this EO do not serve our national interests.

This Executive Order imposes undue burden on members of our community: The people whose status in the United States would be reconsidered under this EO are our students, friends, colleagues, and members of our communities. … This measure is fatally disruptive to the lives of these immigrants, their families, and the communities of which they form an integral part. It is inhumane, ineffective, and un-American.

These bans, as proposed, have consequences that reach beyond the scope of national security. The unethical and discriminatory treatment of law-abiding, hard-working, and well-integrated immigrants fundamentally contravenes the founding principles of the United States.

This article has been updated with the correct name for the National Academies of Sciences, Engineering, and Medicine.