A federal judge has temporarily blocked a Florida law that prevents cruise lines from requiring passengers to prove they’re vaccinated against COVID-19, saying the law appears unconstitutional and won’t likely hold up in court.

The “vaccine passport” ban signed into law in May by Republican Gov. Ron DeSantis fails to protect medical privacy or prevent discrimination against unvaccinated people, but it does appear to violate the First Amendment rights of Norwegian Cruise Lines, U.S. District Judge Kathleen Williams wrote.

In a nearly 60-page ruling issued late Sunday, the judge said Florida failed to “provide a valid evidentiary, factual, or legal predicate” for banning requirements that passengers prove they’ve been vaccinated. Norwegian has shown that suspending the requirement will jeopardize public health, potentially causing “super-spreader” events wherever passengers disembark, she wrote.

Florida separately sued the U.S. Centers for Disease Control and Prevention seeking to block federal cruise ship vaccination requirements. The CDC lost on appeal, but then made its guidelines non-binding, and all cruise lines operating in Florida have agreed to keep following the CDC’s instructions on a voluntary basis, the judge wrote.

The CDC’s current guidelines, in effect until Nov. 1, say cruise lines can sail again with confirmation that at least 95 percent of passengers and crew have been vaccinated, the judge noted.

The plaintiffs are Surgeon General Scott Rivkees and the Florida Department of Health. The state’s attorney, Pete Patterson, previously said the law’s aim is to prevent invasions of privacy and discrimination against passengers who don’t get vaccinated.

DeSantis spokesperson Christina Pushaw said the state will appeal Williams’ ruling. “A prohibition on vaccine passports does not even implicate, let alone violate, anyone’s speech rights, and it furthers the substantial, local interest of preventing discrimination among customers based on private health information,” the statement said.

The pandemic has cost Norwegian more than $6 billion to date by forcing the company to dock its entire 28-vessel fleet and send nearly 30,000 crew members home. Each canceled seven-day voyage would cost the company another $4 million, the judge noted.

The Norwegian Gem is set to depart from Miami on Sunday — the company’s first voyage from Florida since the pandemic halted its operations. More than 1,200 passengers have already booked tickets, promising to prove they’ve been vaccinated before boarding, the judge noted.

“We want nothing more than to sail from Miami, the Cruise Capital of the World, and from the other fabulous Florida ports,” Frank Del Rio, president and CEO of Norwegian Cruise Line, said in a statement. “We welcome today’s ruling that allows us to sail with 100% fully vaccinated guests and crew which we believe is the safest and most prudent way to resume cruise operations amid this global pandemic,

Norwegian said that if it can’t maintain its vaccination policy in Florida, it will have to cancel all voyages leaving from the state or allow unvaccinated passengers on board, and both options would cause significant financial and reputational harm.

The entire business model of cruising depends on ships being able to cross federal, state, local and international jurisdictions in days or even hours, and each of them have different laws, regulations, and protocols, the judge noted. Belize, the Bahamas, the British Virgin Islands and Honduras are among the foreign ports that require proof of vaccination to enter without quarantines or testing.

This landscape of protocols is changing so markedly and frequently, especially as the delta variant becomes more widespread, that it’s “not only impractical, but also financially, legally and logistically onerous” for cruise lines to comply without documentary proof of vaccinations, the ruling says.

The Florida law threatens fines of up to $5,000 per violation, but it fails to prevent discrimination or violations of medical privacy, since businesses can still discourage the unvaccinated in other ways, by posting “vaccinated customers only” signs, or by doing what some other cruise lines now do: They require onerous on-board COVID tests and banish unvaccinated passengers from on-ship activities and ports of call, the ruling says.

As for privacy, Royal Caribbean punches a hole in the pass of unvaccinated patrons, and segregates them from others in the main dining room, the judge noted.