President Donald Trump has banned travel to the U.S. by citizens of 12 countries and restricted access for those from seven others, citing national security concerns in resurrecting and expanding a hallmark policy from his first term that will mostly affect people from Africa and the Middle East.

The ban announced applies to citizens of Afghanistan, Myanmar, Chad, the Republic of Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen. The heightened restrictions apply to people from Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela who are outside the U.S. and don’t hold a valid visa.

The policy took effect Monday and does not have an end date.

Here’s what to know about the new rules:

How Trump justified the ban

Since returning to the White House, Trump has launched a campaign of immigration enforcement that has pushed the limits of executive power and clashed with federal judges trying to restrain him.

In a video posted on social media, Trump tied the new ban to a terrorist attack Sunday in Boulder, Colorado, saying it underscored the dangers posed by some visitors who overstay visas. The man charged in the attack is from Egypt, a country that is not on Trump’s restricted list. U.S. officials say he overstayed a tourist visa.

Who is exempt from the ban

1. Green card holders

2. Dual citizens, including U.S. citizens who also have citizenship of one of the banned countries

3. Some athletes: athletes and their coaches traveling to the U.S. for the World Cup, Olympics or other major sporting event as determined by the U.S. secretary of state

4. Afghans who worked for the U.S. government or its allies in Afghanistan and are holders of Afghan special immigrant visas

5. Iranians belonging to an ethnic or religious minority who are fleeing prosecution

6. Certain foreign national employees of the U.S. government who have served abroad for at least 15 years, and their spouses and children

7. People who were granted asylum or admitted to the U.S. as refugees before the ban took effect

8. People with U.S. family members who apply for visas in connection to their spouses, children or parents

9. Diplomats and foreign government officials on official visits

10. Those traveling to U.N. headquarters in New York solely on official U.N. business

11. Representatives of international organizations and NATO on official visits in the U.S.

12. Children adopted by U.S. citizens

Which countries are affected

Trump said nationals of countries included in the ban pose “terrorism-related” and “public-safety” risks, as well as risks of overstaying their visas. He also said some of these countries had “deficient” screening and vetting or have historically refused to take back their citizens.

His findings rely extensively on an annual Homeland Security report about tourists, businesspeople and students who overstay U.S. visas and arrive by air or sea, singling out countries with high percentages of nationals who remain after their visas expired.

“We don’t want them,” Trump said.

The State Department instructed U.S. embassies and consulates on Friday not to revoke visas previously issued to people from the 12 countries listed in the ban.

In a cable sent to all U.S. diplomatic missions, the department said “no action should be taken for issued visas which have already left the consular section” and that “no visas issued prior to the effective date should be revoked pursuant to this proclamation.”

However, visa applicants from affected countries whose applications have been approved but have not yet received their visas will be denied, according to the cable, which was signed by Secretary of State Marco Rubio.

And, unless an applicant meets narrow criteria for an exemption to the ban, his or her application will be rejected starting on Monday.

How the ban differs from 2017’s

Early in Trump’s first term, he issued an executive order banning travel to the U.S. by citizens of seven predominantly Muslim countries, including Iraq, Syria, Iran, Sudan, Libya, Somalia and Yemen.

It was one of the most chaotic and confusing moments of his young presidency. Travelers from those nations were either barred from getting on flights to the U.S. or detained at U.S. airports after they landed. They included students and faculty, as well as businesspeople, tourists and people visiting friends and family.

The order, often referred to as the “Muslim ban” or the “travel ban,” was retooled amid legal challenges until a version was upheld by the Supreme Court in 2018.

That ban affected various categories of travelers and immigrants from Iran, Somalia, Yemen, Syria and Libya, plus North Koreans and some Venezuelan government officials and their families.

Reactions to Trump’s order

Venezuela President Nicolás Maduro’s government condemned the travel ban, characterizing it in a statement as a “stigmatization and criminalization campaign” against Venezuelans.

Chad President Mahamat Deby Itno said his country would suspend visas for U.S. citizens in response to the ban.

Aid and refugee resettlement groups also denounced it.

“This policy is not about national security — it is about sowing division and vilifying communities that are seeking safety and opportunity in the United States,” said Abby Maxman, president of Oxfam America.

But reactions to the ban ran the gamut from anger to guarded relief and support.

In Haiti, radio stations received a flurry of calls Thursday from angry listeners, including many who said they were Haitians living in the U.S. and who accused Trump of being racist, noting that the people of many of the targeted countries are Black.

Haitian-American Elvanise Louis-Juste, who was at the airport Sunday in Newark, New Jersey, awaiting a flight to her home state of Florida, said many Haitians wanting to come to the U.S. are simply seeking to escape violence and unrest in their country.

“I have family in Haiti, so it’s pretty upsetting to see and hear,” Louis-Juste, 23, said of the travel ban. “I don’t think it’s a good thing. I think it’s very upsetting.”

William Lopez, a 75-year-old property investor who arrived from Cuba in 1967, supports the travel ban.

“These are people that come but don’t want to work, they support the Cuban government, they support communism,” Lopez said at a restaurant near Little Havana in Miami. “What the Trump administration is doing is perfectly good.”

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Associated Press reporters Evens Sanon in Port-au-Prince, Haiti, and Dánica Coto in San Juan, Puerto Rico, Regina Garcia Cano in Caracas, Venezuela, Steve Karnowski in Minneapolis and Gisela Salomon in Miami contributed.