At stake is whether EU vessels have the right to catch snow crab, whose meat is considered a delicacy by gourmets in Japan and South Korea, in the same way than Norwegian vessels do.
"If the Supreme Court thinks the Svalbard treaty applies, it is not only about snow crab, it will be about oil, gas, minerals and fish," he told Reuters.
In a sign of the importance the case has for Norway, 16 Supreme Court judges were present on Tuesday to hear arguments during the four-day session.
"The key question here is the Svalbard Treaty and the surrounding areas," Hallvard Oestgaard, representing the Latvian fishing firm, told the court in his opening statement.
In 2019 the Supreme Court ruled unanimously that EU fishermen must ask permission from Oslo to catch snow crab, after the same Latvian fisheries company had tried to fish off Svalbard with only an EU licence.