Norwegian Cruise Line Holdings is warning it will not be able to resume sailing next month unless a US federal court steps in and suspends a Florida law blocking businesses from asking for proof of Covid-19 vaccination.

The Frank Del Rio-led cruise major filed suit on Tuesday asking the US federal court for the Southern District of Florida to issue an injunction preventing the state from enforcing the prohibition against it, which could result in $5,000 per passenger fines.

In a statement, Norwegian said it had been in discussions with Florida on a method for verifying passengers' vaccination status.

"Despite the ongoing global pandemic and the accelerating spread of the delta variant, Florida continues to prohibit us from requiring vaccine documentation which we believe would enable us to resume sailing in the safest way possible," the company said.

"We believe Florida’s prohibition is on the wrong side of federal law, public health, science and is not in the best interest of the welfare of our guests, crew, and the communities we visit, therefore, we have reluctantly turned to the courts for relief."

Norwegian was set to begin sailing the 2,394-berth Norwegian Gem (built 2007) on 15 August from Miami, with other ships returning to operation later.

In the lawsuit, which names Florida's surgeon general Scott Rivkees as the sole defendant, the company said several of the Norwegian Gem's destinations required all those disembarking to be fully vaccinated.

That coupled with the spread of the delta variant pushed the company to require all passengers and all crew members to be fully vaccinated, greater than the 95% threshold for both groups the US Centers for Disease Control (CDC) laid out for cruise lines in May.

Norwegian argues Florida's law is preempted by federal law and violates first amendment speech protections, as it is a content-based restriction on noncommercial speech.

It said preventing the disclosure of vaccination status could force it from Florida, as it would put passengers, crew and the residents of the places its ships call in danger.

The Florida Department of Health, which Rivkees runs as state surgeon general, did not immediately return a request for comment.

The 2,394-berth Norwegian Gem (built 2007) sails in Rhode Island in 2018. The ship is set to sail from Miami in August in Norwegian Cruise Line's return to sailing after the Covid-19 shutdown. Photo: Ron Cogswell/Creative Commons 2.0

Friends or foes?

Norwegian's lawsuit against Florida comes after the company and industry appeared to have a cordial relationship with the state.

In announcing several new itineraries ahead of its 15 August return to sailing, Norwegian chief executive Del Rio thanked Florida Governor Ron DeSantis, a Republican, for "for fighting in support of our industry".

Del Rio credited DeSantis' efforts as bringing the CDC to the table and hashing out workable regulations for sailing.

The new rules came after Florida sued the CDC in April, with the state arguing the federal agency's strict rules brought the cruise industry to the brink of financial ruin.

The Federal Maritime Commission said the suspension of cruising in March 2020 cost Florida $3.2bn through September and put thousands of cruise workers on unemployment.

Then, DeSantis said the lawsuit was necessary to prevent federal overreach. He said there was no law giving the CDC the ability to shut down an entire industry.