WASHINGTON, July 10, 2025 (AFP) - The US Supreme Court blocked Florida on Wednesday from enforcing a law that would make it a crime for undocumented migrants to enter the southern state.

A federal district judge had put the law on hold in April on the grounds it constituted state interference with federal immigration policy.

An appeals court upheld the ruling by Judge Kathleen Williams and the Supreme Court, in an unsigned order with no explanation, agreed to maintain the block on the law for the time being.

The law, which was signed in February by Florida's Republican governor, Ron DeSantis, calls for prison sentences for undocumented migrants who repeatedly enter the state.

Similar laws have been blocked by federal courts in four other states following challenges from immigrant rights groups.

The Supreme Court order was welcomed by the American Civil Liberties Union (ACLU).

"This ruling affirms what the Constitution demands -- that immigration enforcement is a federal matter," Bacardi Jackson, executive director of the ACLU of Florida, said in a statement.

"Florida's attempt to bypass federal authority and weaponize local law enforcement to police immigration status was not only unlawful, but it also put thousands of people at risk of unjust detention, separation, and abuse."

President Donald Trump campaigned for the White House on a pledge to deport millions of undocumented migrants and DeSantis has also taken a tough stance on immigration.

Trump toured a new Florida migrant detention center -- dubbed "Alligator Alcatraz" -- with DeSantis last week, boasting about the harsh conditions and joking that the reptilian predators will serve as guards.