Donald Trump's Immigration Plan Would Ban One-Third of the World From the U.S.

If Donald Trump were to follow through on his immigration and counterterrorism plans in full, foreign policy experts predict that the presumptive Republican nominee would block out more than a third of the globe — easily including major United States allies.

Combining Trump's proposal to cut immigration from countries with a clear record of terrorist ties and his plan to ban all Muslims from entering the U.S., experts say as many as 70 countries could face major restrictions, impacting billions of people worldwide.

"Certainly using Trump's current rhetoric, we would alienate immediately half of the European Union, a good chunk of the African continent and the Middle East," said Michael Shank, a foreign policy expert and professor at New York University's Center for Global Affairs. "And he's not even talking about cyber terrorism."

Trump first unveiled new details to his counterterrorism plan in June, pledging to suspend even legal immigration from countries known to harbor extremist activity. But when pressed by reporters to outline the exact scope of his ban, Trump has repeatedly kept his answers vague.

"They have a list of terror nations," Trump told NBC News while on a trip to Scotland. "Look it up."

So we did.

There are three names currently on the U.S. State Department's list of countries that sponsor terrorism: Iran, Syria and Sudan. As of just over a year ago, Cuba was on that list too.

The State Department also has a list of countries that are not outright sponsors of terrorism, but are still considered safe havens for extremist activities. The list is fluid and updated frequently, but the latest agency ranking includes Iraq, Lebanon, Yemen, Mali, Mauritania, Somalia, Afghanistan and Pakistan.

This is where Trump's criteria gets tricky to pin down. The list of countries monitored by the State Department is not always clear-cut, often because terrorism by nature is not confined by borders. An example would be al-Qaida, which made a global strategy out of setting up terror cells in different countries throughout a single region.

"The nature of terrorism completely confuses Trump's theory," Shank said. "The very act of terrorism is that it is not adhering to state boundaries."

The lack of clear boundaries becomes an issue in places like Paraguay and Brazil, where some communities are known to harbor extremist activity, but terrorism is not widespread throughout the country. The same goes for Malaysia, Indonesia and the Philippines, where safe havens for terrorists are connected by sea.

Other questions arise when addressing countries like Colombia and Venezuela, which are on the State Department's radar because of guerrilla warfare, notably linked to the Revolutionary Armed Forces of Colombia—People's Army, or FARC.

Trump has since emphasized that he wants to focus his ban on countries with a record of "Islamic terror."

However, even if Trump does narrow his focus, Thomas Wright, an expert in national security and U.S. alliances currently with the Brookings Institute, says that the proposal would still be "remarkably broad."

Key ally countries like the U.K., France, Belgium, Germany, India and Israel could easily fall into Trump's plan to restrict immigration from countries with a history of "Islamic terror," Wright said.

"The reason is that many Western countries have a record of indigenous jihadism from second generation citizens," he said in an email.

This issue of so-called "homegrown jihadism" has been a major factor in a string of recent terror attacks that have roiled Europe in recent years. Assailants, born in Western countries, would train with terror groups abroad and then return home to attack their fellow European citizens.

Western countries have battled this brand of extremism for years, seeking ways to de-escalate tensions from within before tragedy strikes. But would the U.S., under a Trump presidency, be willing to block off immigration from its closest allies?

This uncertainty extends to Trump's well-documented proposals to temporarily ban all Muslims from even traveling to the United States. There are 1.6 billion people who identify as Muslim worldwide, and more than 50 countries in the world where the majority of citizens are Muslim. That figure doesn't even include other countries that have a smaller, yet still sizable share of Muslim citizens. Beyond the practical and legal issues linked to the ban — including difficulties in identifying a person's faith and the constitutional questions surrounding a religion test — what Trump is proposing is remarkable.

Trump has repeatedly waffled on sticking to the fine print of his ban, indicating that he would be open toward accepting certain Muslims into the U.S., but not others. If Trump is serious about blocking out people from a huge portion of the globe, his potential presidency would likely once more place the United States in uncharted territory, at odds with not just allies but with its own supreme law.