A federal judge on Wednesday temporarily blocked part of a Florida law that criminalized transporting into the state anyone who lacked lawful immigration status.

The injunction throws into question a key enforcement component of the law, which went into effect last July and was championed by Gov. Ron DeSantis as he ran for the Republican nomination for president.

The law was intended to discourage unauthorized immigrants from living and working in the state, and organizations that work with immigrants say many undocumented workers have left the state in recent months.

The Farmworker Association of Florida sued the state in July 2023, alleging the law was unconstitutional. The organization said that its members would be separated from their families, unable to receive lifesaving medical appointments and prevented from driving to immigration agencies overseeing their cases. They risked jail time if they did so.

The judge in the case, Roy K. Altman of the U.S. District Court for the Southern District of Florida, rejected the plaintiffs’ argument that the law was unconstitutionally vague. But he was persuaded that in criminalizing the transport of undocumented immigrants, the state was usurping federal authority over immigration.

In his ruling, invoking the Immigration and Nationality Act and a previous ruling by the 11th Circuit Court of Appeals, he wrote that “this framework allows the federal government to retain control over enforcement.”

Judge Altman was confirmed to the federal bench in 2019 after being nominated by President Donald J. Trump.

In recent months, several states have passed bills to crack down on undocumented immigration, including Texas, Oklahoma and Iowa, which are all facing legal challenges.

“This decision on the Florida law is yet another blow to an attempt by states to take over federal immigration enforcement,” said Kathleen Bush-Joseph, a policy analyst at the Migration Policy Institute.

Mattathias Schwartz contributed reporting.