President Trump on Wednesday signed a travel ban on 12 countries, primarily in Africa and the Middle East, reviving an effort from his first term to prevent large numbers of immigrants and visitors from entering the United States.

Here is a closer look at why the administration says it is instituting full bans on foreign nationals traveling to the U.S. from 12 nations.

The effort comes as the president has pursued extraordinary measures to curtail legal and illegal immigration.

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An aid organization that has sent more than 100 Haitian children with serious cardiac conditions to the U.S. for heart surgery said President Donald Trump’s travel ban will stall or cancel lifesaving procedures.

More than 24,000 international students from the affected countries studied in the U.S. as recently as the 2023-2024 academic year.

The American Jewish Committee has come out against President Donald Trump’s new executive order banning travel to the United States from 12 countries, which Trump says is needed because of incidents such as this week’s attack on a rally for the release of Israeli hostages in Boulder, Colorado.

Immigration order restricting travel from 19 nations could prove difficult to challenge legally, with one attorney noting its broader scope compared to the 2017 Muslim ban.