How a little-known law became Trump's weapon of choice against immigration

Vox

10-06-2025

covers politics Vox. She first joined Vox in 2019, and her work has also appeared in Politico, Washington Monthly, and the New Republic.
Demonstrators gather to protest against a sweeping new travel ban announced last week by President Donald Trump, outside Los Angeles International Airport on June 9, 2025. Patrick T. Fallon/AFP via Getty Images
President Donald Trump can't stop using — and abusing — his legal authority to block the entry of noncitizens into the country.
When he issued a travel ban on citizens of Muslim-majority countries early in his first term, he did so by invoking Section 212(f) of the Immigration and Nationality Act, which allows him to block any foreigner if he deems that their entry would be 'detrimental to the interests of the United States.'
When he issued a proclamation turning away noncitizens who could not demonstrate the ability to pay for their health care costs, he cited Section 212(f).
When he halted most legal immigration at the beginning of the Covid-19 pandemic, first from China and then from other countries, there was Section 212(f) again.
Finally, last week, he announced that he would block foreign students from receiving student visas to attend Harvard and implement a travel ban on 12 countries, as well as restrictions on seven others. The travel ban took effect on Monday, just after midnight, and the legal framework for both orders was built on Section 212(f).
Some of Trump's attempts to invoke Section 212(f) have been challenged in court. Judges struck down several versions of Trump's first-term travel ban before the third iteration was ultimately upheld by the US Supreme Court (after it was expanded to include non-Muslim-majority countries). President Joe Biden rescinded the travel ban, as well as the Covid-19 and health care-related bans, when he took office, refusing to defend them in legal challenges.
Most recently, a federal judge in Massachusetts also blocked Trump's order on Harvard students, and as of Monday, the State Department had returned to processing international student visas.
However, in testing the limits of 212(f) through these policies, Trump has succeeded in getting the Supreme Court to affirm his broad powers to ban foreign nationals under immigration law, marking a key expansion of executive authority.
While previous presidents invoked Section 212(f), none of them did so as frequently or as aggressively as Trump. The law has become a key tool to keep people out as Trump tries to implement his restrictive vision of US immigration policy.
How Trump expanded presidential powers to ban foreigners
Before Trump, both Democratic and Republican presidents used the 212(f) authority sparingly. It was typically employed in order to enforce United Nations sanctions or target individuals or groups associated with terrorism, human rights violations, drug trafficking, or specific international crises.
Former President Barack Obama, for instance, used the authority to block Russian officials from entering the US following their country's 2014 invasion of Crimea.
Former President George W. Bush used it to block Syrian officials after the 2005 assassination of the Lebanese prime minister at the hands of the Syrian-backed militant group Hezbollah, which the US designates as a terrorist organization.
Former President Bill Clinton used it to impose restrictions on Nigerian military officials who impeded the country's transition to democracy by annulling the country's 1993 elections.
Trump's conceptualization of 212(f), however, is markedly different. He has used the authority to block broad swaths of noncitizens from a variety of countries, not just their government officials or people involved in criminal activity. He has not spared US visa or green card holders in some cases, including those affected by his first travel ban.
That has created a new legal paradigm that has afforded the president sweeping powers to keep immigrants out.
The Supreme Court's 2018 decision narrowly upholding Trump's first travel ban made that shift clear. Chief Justice John Roberts wrote in the majority opinion that Section 212(f) 'exudes deference to the President in every clause.' For that reason, the court refused to question the superficial national security rationale Trump provided for the travel ban.
That's despite substantial evidence that the actual motivation behind the ban was, as Justice Sonia Sotomayor put it in the dissent, 'anti-Muslim animus' that violated the Constitution's religious liberty protections. That evidence included Trump's 2015 campaign statements calling for 'a total and complete shutdown of Muslims entering the United States,' which lower-court judges pointed to in blocking earlier versions of the travel ban in 2017.
The question is whether the justices will again defer to Trump if the new travel ban and ban on international students at Harvard come before the Supreme Court.
According to Stephen Yale-Loehr, a retired immigration law professor at Cornell Law School, 'court challenges to this travel ban are likely, but they may fail.' However, Yale-Loehr said, 'even if this expansion is legal, it is not good policy. We are not necessarily safer by banning immigrants from these countries.'
Notably, the new travel ban includes exemptions for green card holders, noncitizens from affected countries who are already in the US, and athletes from the affected countries competing in international competitions like the Olympics. He's also invoked the potential for visa overstays, in addition to the usual national security grounds, in the rationale for his latest ban.
All of that might help Trump's case if the policy is challenged in court. Unlike a blanket ban on immigrants from the affected countries, it is tailored to withstand legal scrutiny by targeting only would-be immigrants who are currently not in the US. Additionally, the ban's invocation of national security concerns puts it in territory where the president has generally been afforded considerable discretion by the courts. (A fact he has taken advantage of in issuing a flurry of national emergency declarations on all sorts of issues.)
Given the particulars of the new ban and the administration's previous history before the Court, some immigrant advocates have turned to Congress, rather than the courts, to intervene. They are asking for a legislative fix to stop Trump from implementing policies that will affect both US citizens who might be separated from their families and citizens of foreign countries hoping to enter the US, though such a measure would almost certainly have to wait on unified Democratic control of government.