Hawaii authorities may have been violating their own state law for years by issuing commercial fishing licenses to thousands of foreign workers who were refused entry into the country, the Associated Press has found.

About 700 of these men are confined to vessels in Honolulu, some making less than $1 an hour to catch premium tuna and swordfish sold at some of America’s most upscale restaurants and grocery stores.

In this unique fishing arrangement, Hawaii’s boat owners pay brokers up to $10,000 for each crew member sent from abroad. Because the workers don’t have visas, they aren’t allowed to arrive at Honolulu’s airport. Instead, they’re flown to foreign ports and put on fishing boats for long sails back to Hawaii.

Before they start working, they need a commercial fishing license. And in order to get that, Hawaii requires that they are “lawfully admitted” to the U.S. As proof of legal admission, state officials point to landing permits issued to all fishermen by U.S. Customs and Border Protection agents when the men arrive at the dock.

Here’s the hitch: AP has learned Customs agents stamp “refused” on all the landing permits, which voids them. So instead of being “lawfully admitted,” the fishermen are actually barred by law from setting foot in the U.S.

“Try taking a check to your bank that says ‘void’ on it and telling them, ‘Oh, but they wrote the check to me,’” said Hawaii attorney Lance Collins, who advocates for the workers.

Nonetheless, in a written opinion, state Attorney General Douglas Chin said the Department of Land and Natural Resources provides the landing permits as proof the fishermen are “lawfully admitted.”

Customs sees it differently. “NO. They cannot be admitted,” spokesman Frank Falcon wrote in an email.

The Hawaii Longline Association has condemned labor abuses. Its president, Sean Martin, would not comment for this story, but in the past the group said the crew members are legally hired for legitimate work on the fleet’s 141 active vessels. And while the conditions and pay are often below U.S. standards, the jobs are typically better than the bleak opportunities the men have at home, mostly in the Philippines, Vietnam, Indonesia and the tiny Pacific island of Kiribati.

Under federal law, U.S. citizens must make up 75 percent of the crew on most American commercial fishing boats. An AP investigation last year revealed Hawaii’s fleet — which catches about $110 million worth of seafood annually — relies on a federal loophole allowing foreign fishermen to fill most jobs.

On some boats the men are exposed to dangerous, unsanitary conditions. Two workers who ran away in San Francisco were granted visas as victims of human trafficking in 2010. They are now suing their boat owner.

Hawaii’s premium fish is sold everywhere from Costco and Sam’s Club to Trump International Hotel Waikiki. Whole Foods suspended buying seafood from the fleet after the AP’s initial report, while Costco says it is monitoring the situation. Trump Hotel and Wal-Mart, which owns Sam’s Club, did not respond to requests for comment.

The Hawaii Seafood Council recently surveyed crew members and assessed the fleet’s working conditions. A draft of the findings, published online, finds some fishermen have contracts requiring them to pay for replacement workers if they break their agreements, or facing $5,000 fines for absconding — more than a year’s salary for some.

“There exists no system of grievance mechanisms for crew to voice concerns over pay,” the report says.

However, the assessment also found some fishermen had excellent relationships with their captains. All 207 men surveyed said they were being paid in cash, and none expressed concerns about forced labor or human trafficking.

In Honolulu most vessels dock at piers 17 and 38, which are guarded and patrolled, but some go as far as the West Coast.

Customs says six fishermen were deported in 2016 after wandering away from their boats in Honolulu, some to visit friends on other vessels, others sneaking away for a drink.

Immigration and Customs Enforcement spokeswoman Virginia Kice said agents checking out a number of leads related to possible human trafficking in the fleet have “identified instances where crew members were contending with less than ideal working conditions,” but found no situations meeting the legal threshold to bring criminal charges.

Some fishermen have good working conditions, but others lack clean drinking water or proper health care, and are fed just bait and rice, according to federal marine observers, who live with the men for weeks at a time. Many crew members are forced to use buckets as toilets.

Uli Kozak, an Indonesian-language professor at the University of Hawaii, said the men have spoken of physical abuse, including captains slapping them in the face. Sometimes when he visits to exchange goods for fresh fish, workers ask him to bring vegetables because of shortages on board, he said.

“Very often they are in a situation where they have no choice,” Kozak said. “They are here, they signed their contract and they have to work until the contract finishes.”