Here's the petition, still open for signatures.
Academics against immigration executive order
And here's a story in the Washington Post that explains some of the issues that particularly concern academics in our professional roles (and not just as American patriots committed to the freedom of ideas and many other freedoms).
12 Nobel laureates, thousands of academics sign protest of Trump immigration order
"What’s at stake, said Emery Berger, a professor in the College of Information and Computer Sciences at the University of Massachusetts Amherst, who is not one of the organizers of the petition but supports the effort, begins with free exchange of information.
"But there’s more. He said he has already heard academics overseas planning to avoid, or boycott, conferences in the United States. “It’s very chilling,” he said.
"Students are horrified, he said, 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."