Throughout the 2024 presidential election, President Donald Trump campaigned on carrying out the “largest deportation in American history.” During his inaugural speech, he stated he would announce a national emergency at the border, bring back “Remain in Mexico,” send troops to the border, and use a 1798 law to pursue his immigration agenda. With all that in mind, how will President Trump carry out mass deportations?

Since his first run for president in 2016, immigration has been top of mind for Trump. He created the “Remain in Mexico” policy, which told asylum seekers to stay in Mexico until their court date in the United States. It was highly criticized for putting innocent immigrants into harm’s way as they waited for a chance for safe harbor in the U.S. before it was reversed under President Biden.

Even more controversial was Trump’s child separation policy. In 2018, Thomas Homan, now Trump’s Border Czar (unofficial lead advisor on border affairs), created the “zero tolerance” policy on immigration, which included the child separation policy. It instructed border officials to prosecute all adults crossing the border and then separate them from their children. Homan has stated that child separation “needs to be considered” in the second Trump administration.

Yet the policy that caught the most attention during Trump’s inaugural address was when he announced his intention to use the Alien Enemies Act of 1798 to carry out these significant deportations. The law allows a president to detain and deport natives or citizens of an enemy nation. According to the Brennan Center for Justice, the law allows the president to “target these immigrants without a hearing and based only on their country of birth or citizenship.” The president can use the law during a “declared war” or an attempted invasion of the United States. In the past, it was used to intern Japanese immigrants during World War Two. Trump is claiming that the level of immigrants crossing the southern border amounts to an invasion, and therefore, he has the authority to use the law.

One of Trump’s spokespeople, Karoline Leavitt, has stated that the new administration would “marshal every federal and state power to institute the largest deportation” in history. How large would the deportation be? Trump has claimed that he will deport between 15 and 20 million people during the next four years. However, to accomplish this, Trump would have to spend over $300 billion on infrastructure to evict that amount of immigrants, according to the American Immigration Council (AIC). Even if Trump can deport that many immigrants, its effects on the economy would be unprecedented. According to the AIC, the economy would decrease by over 4% because of the loss of workers in key sectors.

Trump’s plans have been severely criticized by human rights groups like the American Civil Liberties Union (ACLU), which stated that his administration would be pursuing “cruelty, overt racism, and deeply damaging policies.” Organizations like the ACLU will most likely challenge these policies in court, with some cases potentially reaching the Supreme Court. Even if these policies are found to be legal, it is doubtful that Trump could deport almost 20 million immigrants in just four years. However, by pursuing these incredibly ambitious and controversial policies, the Trump administration is ensuring that immigration will remain one of the most dividing political issues for decades to come.