For years, Iran has led the U.S. State Department's list of state sponsors of terrorism, and so it is not unusual that Iranian scientists would face extra scrutiny from security officials, especially given concerns about nuclear proliferation in Iran. However, like the other countries affected by the ban, no immigrants from Iran have carried out terrorist attacks on U.S. soil between 1975 and the end of 2015. And given the blanket nature of the ban, it affects many scientists who have nothing to do with nuclear research.

Asgari is only one of hundreds of scientists who have been affected by Trump’s ban, which also applies to green-card holders who have permanent residence in the U.S., but have gone overseas for professional or personal reasons. That includes Ali Abdi, an Iranian Ph.D. student studying anthropology at Yale University. A few hours after taking part in the Women’s March in Washington, D.C., he left the U.S. to do ethnographic research in Afghanistan. He’s now stuck in Dubai, awaiting a visa from the Afghan consulate. If that falls through, he doubts he can return to the U.S. despite having a green card, and he rules out a return to Iran because of his record of civil-rights activism. “Let see how things unfold in the U.S.,” he says. “I am sure people around the globe will resist.”

Some already have. On Friday afternoon, thousands of academics, including a dozen Nobel laureates, signed a petition protesting Trump’s order. On Saturday, thousands of protesters filled airports in half-a-dozen major U.S. cities. On a Twitter account called @FreeSciNet, Jen Golbeck from the University of Maryland started building a network to support scientists who were blocked from re-entry, helping them with parked cars, untended pets, and more. The ACLU also sprang into action. In response to their petition, federal judge Ann Donnelly issued a nationwide stay, decreeing that anyone who had already arrived at U.S. airports with valid visas would be allowed to remain; three other judges followed suit. But these measures are temporary. They don’t undo the full executive order, which the Department of Homeland Security has said it will “continue to enforce.” And they don’t apply to future arrivals.

“Many talented friends of mine can’t come back to finish their degrees, simply because they went back to their hometowns to visit their parents,” says Saeed Mehraban, an Iranian Ph.D. student who is working on quantum computing at MIT, and is currently in Austin visiting his advisor. “I’m just taking a domestic flight from Texas to Boston, and I’m still scared they may do me harm.”

“Professional and personal lives are being destroyed,” says Josh Plotkin from the University of Pennsylvania. One of his postdoctoral fellows—an Iranian, and a legal permanent resident of the U.S.—was traveling abroad when Trump’s order was signed. “They are now separated from their spouse, and likely unable to attend faculty job interviews that are scheduled in the coming weeks. This postdoc was working on new ways to treat HIV/AIDS.”