Agents from Norway's Data Protection Authority raided the Irish airline's premises unannounced to inspect the cameras, which were installed this January.
“They have set up multiple cameras,” Bjørn Erik Thon, the head of the authority, told Norwegian state broadcaster NRK. “The rule is that you cannot film more than is strictly necessary for security."
The authority has submitted a report arguing that Ryanair failed to apply for permission to film employees, filmed more than necessary to prevent theft, and stored the images for too long.
The cameras were set up in the building where employees receive shift information, eat meals, and store money from sales onboard flights.
Ryanair has argued that the cameras were needed to prevent theft of cash collected from onboard sales, and that the building is subject to Irish rather than Norwegian law, claims Thon rejected.
"In that case, you should install a safe to prevent burglary," he said of the theft risk. "Then you only need to film the safe. You don't need to film employees when they're eating."
As for the building, he argued that it could not possibly be subject to Irish law. “It’s a location that is in Norway, leased through a contract with an airport in Norway," he said.
The case is the latest in a string of problems faced by the airline in Norway over its treatment of staff in Norway, who are employed under Irish, rather than Norwegian contracts, something the airline argues frees it from local labour laws.
The airline said it did "not comment on pending administrative matters".