The plaintiffs — five Norwegians, an Icelander and a Swede — are today aged between 51 and 70 and say they suffer from severe lung, brain and hearing problems that were triggered by decompression accidents during dives dating between the 1970s and the 1990s.
The divers contend that Norwegian authorities failed to adequately regulate decompression procedures, a vital process in which a diver gradually returns to normal atmospheric pressure after spending time below the surface.
"The applicants would not have suffered long-term damages had the state taken efficient measures," the lawyer E. Ludvigsen told the European Court of Human Rights in Strasbourg. He did not provide his first name.
Ludvigsen said the state kept decompression tables "both confidential and incomprehensible" and failed to force oil companies to disclose their own data.
The Norwegian government argued it should not be found responsible and said any problems were the fault of the diving companies.
Though Norway harmonized decompression procedures in 1991, the plaintiffs said the government should have acted sooner.
Between 350 and 400 divers worked on test rigs in the 1970s while offshore drilling was in its infancy.
In 2002, an independent report found that such dives were carried out without proper controls.
A judgment in the case is not expected for at least several weeks.