WASHINGTON — The Trump administration’s effort to expand mandatory immigration detention has faced overwhelming resistance in federal court, but the legal fight may be headed toward a Supreme Court that has recently sided with the administration in major immigration disputes. More than 460 federal district judges have ruled roughly 20,000 times against Immigration and Customs Enforcement’s attempt to detain immigrants without giving them an opportunity to seek release on bond, according to a review of court decisions. The administration has also lost in nine of the nation’s 11 regional appeals circuits. The dispute centers on the administration’s interpretation of a 1996 immigration law. The law requires detention for certain people deemed to be “seeking admission” to the United States. For decades, administrations — including President Donald Trump’s first administration — generally applied that provision to people who had recently crossed the southern border. People who entered the country years earlier could still be detained under other provisions, but they generally received bond hearings. At those hearings, an immigration judge could consider whether they posed a danger or flight risk and whether they could remain safely in their communities while their cases proceeded. The Trump administration changed that approach last year. It argued that anyone living in the United States without legal authorization could be classified as seeking admission and therefore subjected to mandatory detention. Courts have said the interpretation could expand the policy to more than 6 million people who previously would have been eligible for bond hearings. District court judges from across the ideological spectrum have largely rejected the government’s position. Many have concluded that Congress did not clearly authorize a detention system of that scale, particularly one that could sweep in people without criminal records who have lived in the country for years and have spouses, children and other deep community ties. The administration’s supporters argue that the law should not favor people who avoided detection after crossing the border over those who presented themselves to immigration authorities. They also contend that the government’s broader use of its statutory authority is not unlawful simply because previous administrations chose not to exercise it. At the appeals-court level, the results have been more politically divided. All but four Republican-appointed appellate judges who considered the issue sided with the administration, while Democratic-appointed judges opposed its position. That pattern could offer the government a more favorable signal as the case moves closer to the Supreme Court, legal observers say. “There’s definitely a split, but I think if you look at the judges who are the closest proxy of a Justice Barrett or a Justice Kavanaugh, they have overwhelmingly sided with the administration on this issue,” said Eric Wessan, Iowa’s chief litigator. Iowa has urged the Supreme Court to uphold ICE’s interpretation. Wessan cited dissents by appeals judges Eric Murphy and Barbara Lagoa, both appointed by Trump, and said they could reflect the position of a likely median vote on the Supreme Court. Jennifer Mascott, another Trump-appointed appeals judge who sided with ICE in the 3rd Circuit, previously clerked for Justice Brett Kavanaugh. Georgetown University law professor Steve Vladeck cautioned that the lower-court split may not predict how the justices will rule. The Supreme Court, he said, has repeatedly declined to follow lower-court consensus and has recently resolved close immigration questions in the administration’s favor. “I wish I were more confident that there’s a majority of justices to follow the overwhelming majority of their lower-court colleagues,” Vladeck said. A ruling for ICE could remove bond hearings for a vast population of immigrants, including many people who have lived in the United States for years and whose families and workplaces are rooted in local communities. Immigrant-rights advocates say detention without individualized review would impose major costs on families and communities, while the administration argues that broader detention is necessary to enforce removal proceedings. Amit Jain, a Supreme Court and appellate counsel at the MacArthur Justice Center, said the lower-court decisions should carry weight because the administration’s theory is both novel and far-reaching. He argued that the interpretation could make other parts of immigration law, including the Laken Riley Act, redundant and raise serious due-process concerns. “The 9-2 split is further proof of how novel the government’s extraordinary policy is,” Jain said. He added that the district courts’ broader rejection may reflect their closer exposure to the consequences of detention for families and neighborhoods. The Supreme Court’s eventual decision will determine whether the administration can impose mandatory detention on a population far larger than those traditionally covered by the law — and whether people facing deportation proceedings retain a meaningful chance to ask a judge for release.