A U.S. appeals court on Friday upheld a decision blocking Iowa from implementing a law that would have allowed for the arrest and prosecution of undocumented immigrants, citing federal supremacy over immigration enforcement.

The St. Louis-based 8th U.S. Circuit Court of Appeals ruled that Iowa’s law, which criminalized “illegal reentry” into the state and authorized state judges to deport individuals after serving prison sentences, would unlawfully interfere with federal immigration policy.

“Decisions about the removal of illegal aliens touch on foreign relations and must be made with one voice,” wrote Circuit Judge Duane Benton in the court’s opinion.

The law, passed by Iowa’s Republican-led legislature, was scheduled to take effect in July but was blocked by a federal district court after the U.S. Department of Justice (DOJ) filed a lawsuit challenging its constitutionality during the Biden administration. The appeals court’s decision keeps the law on hold while litigation continues.

Federal vs. State Control Over Immigration

The court’s decision highlights the ongoing tension between federal and state governments over immigration enforcement. The 8th Circuit emphasized that immigration is primarily a federal responsibility, particularly because it intersects with foreign policy. Allowing Iowa to criminalize unauthorized presence in the state, the court said, would undermine the federal government’s ability to enforce U.S. immigration laws consistently.

Under the blocked Iowa law, undocumented individuals who reentered the state after deportation would have faced up to two years in prison. Additionally, state judges could have ordered deportation upon the completion of a prison sentence, a power traditionally reserved for federal immigration authorities.

The DOJ argued that such measures violated the Constitution’s Supremacy Clause, which holds that federal laws take precedence over conflicting state laws.

Iowa Officials Respond

Iowa Attorney General Brenna Bird, a Republican, criticized the ruling in a statement, framing the blocked law as part of the state’s response to what she called the Biden administration’s failure to address illegal immigration.

“Iowa stood strong against the Biden-Harris border invasion that made every state a border state. And despite today’s court ruling, the battle is far from over,” Bird said.

The Justice Department, now under President Donald Trump’s administration, did not immediately comment on the ruling. Trump, who has made immigration a cornerstone of his agenda, could decide to drop the DOJ’s legal challenge to Iowa’s law, as well as similar lawsuits against immigration-related measures in Texas and Oklahoma.

State-Level Immigration Laws Under Fire

Iowa’s blocked law is part of a broader wave of immigration-related legislation in Republican-controlled states. Frustrated with federal policies under former President Joe Biden, states such as Texas, Oklahoma, and Iowa passed laws aimed at expanding state authority over immigration enforcement.

Civil rights groups have also challenged these laws, arguing that they lead to racial profiling, infringe on federal authority, and violate constitutional protections.

What’s Next?

The appeals court’s decision signals that the federal judiciary is likely to continue curbing state-level immigration laws that overlap with federal powers. However, the issue may ultimately head to the U.S. Supreme Court if Republican-led states and the Trump administration push for broader state authority in immigration matters.