Moody, who endorsed DeSantis’ bid for president, has engaged in a long-running series of battles with the Biden administration, especially over immigration. Moody is widely viewed as a potential 2026 candidate for governor.

DeSantis made Florida’s new union law one of his top priorities during the 2023 session that was supposed to be a springboard to his presidential campaign — an effort that has recently seen him drop to third place or worse in some polls. The law, which took effect on July 1, includes including a prohibition on public employers from deducting union dues from employee paychecks and making it easier to decertify unions.

Critics said the law was aimed at DeSantis’ political enemies — such as Florida’s teacher union — since the provisions did not apply to unions that represent law-enforcement officers and firefighters.

But this latest confrontation was foretold months ago. The bill was changed on the Senate floor to include a potential carve-out from the law for mass transit workers after questions were raised about whether the legislation conflicted with federal labor laws that could put federal funding at risk.

Since the law took effect, local transportation authorities and local governments have asked the state’s Public Employee Relations Commission for waivers from the law after federal officials contended that Florida’s new law conflicts with federal requirements.

The commission, which is overseen by DeSantis appointees, agreed to issue waivers but made them time-limited and conditional. But a top official with the Department of Labor said those types of waivers did not comply. In a late August letter to the state commission, the Florida Public Transportation Association said that more than $800 million in federal funding for mass transit systems was in jeopardy if the commission did not hand out permanent waivers.

Moody’s new lawsuit was filed against the Department of Transportation, the Department of Labor and the Federal Transit Administration as well as top officials in those agencies. It asks a federal judge to block the agencies from withholding federal grants as well as declare unconstitutional the part of the federal law the Department of Labor is relying on to question Florida’s law.

A spokesperson for Buttigieg and the Department of Transportation declined to comment on “ongoing litigation.”

Meanwhile, lawsuits have been filed against Florida’s union law in state courts, including one that alleged it violated collective bargaining rights guaranteed in the state constitution. A circuit judge on Tuesday threw out a lawsuit filed by three South Florida public employee unions and three union members but Judge J. Lee Marsh did leave the door open for the lawsuit to be refiled.