The #MuslimBan is causing panic, chaos, and confusion at airports around the world

The implementation of President Donald Trump’s executive order banning refugees from several Muslim-majority countries is wreaking havoc at airports across the world, and even some travelers legally allowed to reside in the U.S. are being prevented from boarding flights to return home.

Widespread uncertainty over the order is partly due to the Trump administration leaving out several important clarifications on how the measure would be enforced—and against whom. For example, it was immediately unclear if the order would target people with dual nationalities and those who possess green cards.

“Visas being denied immediately. Chaos at airports and in the air. #MuslimBan will apply to green card holders attempting to return tonight,” American-Arab Anti-Discrimination Committee policy director Abed Ayoub tweeted late Friday night.

By Saturday morning, Ayoub had confirmed that people with pending visas from listed countries—Syria, Libya, Iraq, Iran, Somalia, Sudan, and Yemen—were not allowed to board flights back to the U.S.

Department of Homeland Security spokeswoman Gillian Christensen later confirmed that green card holders from the seven listed Muslim-majority countries would be temporarily barred from entering the U.S., despite being legal permanent residents, Reuters reported.

Trita Parsi, who heads the National Iranian American Council, began documenting on Twitter the travel horror stories late Friday night.

Of the seven countries, Iranians would be most affected, according to Ayoub. That includes Iranian director Asghar Farhadi, whose film The Salesman is up for an Oscar for Best Foreign Language Film. Farhadi—who also won an Oscar in 2012—won’t be allowed into the U.S. to attend the Academy Awards, The Hill reported.

“We strongly recommend Iranian green card holders not leave the country until further clarity is achieved,” NIAC stated in an emergency response to the crackdown.

Also on Saturday morning, lawyers scrambled to file an emergency lawsuit to procure the release of two Iraqi refugees detained at JFK International Airport in New York. A third refugee family reportedly was detained at the airport in San Francisco.

Meanwhile, Ayoub is urging local elected officials to go to nearby airports to protest the new draconian measures.