A Burmese American woman was eager to bring her siblings over to the U.S. from Myanmar amid a more than 15-year wait for visas.

President Donald Trump’s new ban on travel to the United States by citizens from 12 mainly African and Middle Eastern countries is now in effect.

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.