U.S. President Donald Trump has invoked the Alien Enemies Act as part of his commitment to deport millions of individuals residing in the country illegally. The proclamation, made public on Saturday, marks a significant move under an act that has been historically used during wartime and periods of national security concern.

Enacted in 1798 during tensions with France, the Alien Enemies Act grants the president authority to deport, detain, or impose restrictions on individuals who are considered a potential security threat due to their allegiance to a foreign power. The law has been applied in various instances throughout U.S. history, particularly during wartime.

President Woodrow Wilson used the act to impose restrictions on citizens of enemy nations during World War I, including prohibiting them from possessing firearms, residing in certain areas, and publishing specific materials. During World War II, President Franklin Roosevelt utilized the act to justify the internment of individuals of Japanese, German, and Italian descent. President Harry Truman continued its use until 1951, even after the war had ended.

In his proclamation, Trump cited the Venezuelan gang Tren de Aragua, which has been designated as a foreign terrorist organization by the U.S. government. He asserted that the gang was engaged in "irregular warfare" and "hostile actions" against the United States with the intent of destabilizing the country. According to the administration, Tren de Aragua has been linked to crimes such as kidnapping, extortion, organized crime, and contract killings, with alleged infiltration into the Venezuelan government.

The Alien Enemies Act has faced legal challenges, with individuals contesting their detention or removal. However, the majority of cases have revolved around questions of citizenship. The law has been upheld as constitutional, with the U.S. Supreme Court affirming that it can be enforced even after wartime.

In a notable 1948 case, the Supreme Court ruled that Kurt Ludecke, a former Nazi who had fled Germany and entered the United States, could be deported under the act despite World War II having ended. The court reasoned that his deportation was impractical during the war itself, reinforcing the government's authority to act under the law beyond wartime.

Democratic lawmakers in the U.S. House and Senate have reintroduced a bill seeking to repeal the act, arguing that its historical use in the internment of individuals violates civil and individual rights.

Beyond declared wars, the Alien Enemies Act allows for its invocation in cases of "invasion" or "predatory incursion." However, courts have been asked to define what constitutes an invasion.

In the 1990s, California filed a lawsuit against the federal government, claiming that the failure to prevent individuals from crossing the southern border illegally amounted to an invasion. The court ruled that determining whether an invasion had occurred was a political decision outside judicial oversight. Additionally, historical interpretations suggest that the term "invasion" was originally understood to mean armed hostility by a foreign state, rather than the movement of individuals across a border.

Trump's decision to invoke the Alien Enemies Act signals a strong stance on immigration enforcement, potentially setting the stage for legal challenges and political debate. While the act has historical precedence, its application in the modern era raises questions about its implications for civil liberties and the broader immigration system in the United States.