Trump's immigration plan raises many unanswered questions

Donald Trump's speech on foreign policy Monday focused in large part on his proposal to suspend immigration from dangerous parts of the world and impose a new system of "extreme vetting" that would subject applicants to questions about their personal ideology.

"We should only admit into this country those who share our values and respect our people," said Trump, proposing what he called an "ideological screening test."

"The time is overdue to develop a new screening test for the threats we face today. I call it extreme vetting. I call it extreme, extreme vetting. Our country has enough problems," he said.

Trump didn't offer many specifics in his speech, raising a number of questions about how he would implement his proposals.

Here a look at some of the questions the Republican presidential nominee didn't answer on Monday:

What does 'extreme vetting' mean?

Trump defined it Monday this way: "In addition to screening out all members or sympathizers of terrorist groups, we must also screen out any who have hostile attitudes toward our country or its principles — or who believe that Sharia law should supplant American law. Those who do not believe in our Constitution, or who support bigotry and hatred, will not be admitted for immigration into our county."

U.S. immigration officials already vet potential immigrants, conducting background checks on those who seek to live or work in America. Visa applicants already must answer questions about whether they have ever engaged in, or intend to engage, in any form of terrorist activity, along with questions such as whether they've ever ordered, incited, called for, committed, assisted, helped with, or otherwise participated in activity that includes "limiting or denying any person's ability to exercise religious beliefs."

What would be different under Trump's plan? To start, aides said, he would consider adding a review of social media accounts and conducting interviews with an applicant's friends and family.

But it's unclear how Trump's system would determine a potential immigrant's position on what could be highly subjective issues. What some may consider to be "support (for) bigotry and hatred" may be, in another person's view, an expression of free speech protected by the First Amendment. That raises questions about where a Trump administration would draw the line.

Who would be subject to the immigration ban?

Trump proposed temporarily suspending immigration "from some of the most dangerous and volatile regions of the world that have a history of exporting terrorism."

Which countries exactly? That's TBD.

Trump says that as soon as he takes office, he would ask the State Department and the Department of Homeland Security to identify "a list of regions where adequate screening cannot take place."

Trump said, "There are many such regions" and vows to "stop processing visas from those areas until such time as it is deemed safe to resume based on new circumstances or new procedures."

Also unclear is whether such a ban would only apply to people seeking to immigrate to the U.S. to live and to work, or would affect tourists, too. Trump used both "immigrants" and "visitors" during his Monday speech, raising the prospect he could scrap an existing waiver program that allows people from friendly countries to visit the U.S. as tourists without a visa.

How much will it cost?

Trump has not broached the topic of how much it would cost to set up and run his new vetting system.

The U.S. already screens everyone who enters the country, said Doris Meissner, who heads the Migration Policy Institute's U.S. immigration policy program.

"The fact of the matter is we have very sophisticated vetting programs in place," she said, noting that the country has invested billions in improving systems and information sharing since the 9/11 attacks.

The costs of an expansion of that system as Trump has proposed, she said, would likely be "extraordinary."

Does he still want to bar Muslims from the U.S.?

Trump's unprecedented call in December 2015 "for a total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what is going on" is still listed on his campaign website, and he has yet to personally denounce the controversial proposal.

Following the June shooting at the Pulse nightclub in Orlando, Florida, Trump appeared to introduce a new standard, vowing to "suspend immigration from areas of the world where there is a proven history of terrorism against the United States, Europe or our allies, until we fully understand how to end these threats."

Trump's aides described the new language as a replacement for the religious test, but Trump has described it differently. "I actually don't think it's a rollback. In fact, you could say it's an expansion. I'm looking now at territory," he said in a July interview with NBC News, suggesting the change was more about language. "People were so upset when I used the word Muslim. 'Oh, you can't use the word Muslim,' remember this? And I'm OK with that, because I'm talking territory instead of Muslim."

Trump had promised to release a list of "terror countries," but never did. His speech Monday referred to regions, with the caveat that he might not name them until after taking office.