A ban on Russian flights over Norway, introduced in reaction to the war in Ukraine, also applies to drones, the Norwegian Supreme Court said in a ruling handed down Friday.
The decision could lead to a retrial of Andrei Yakunin, son of a former close ally of Russian President Vladimir Putin, who was acquitted last year of flying drones over Svalbard during a boat trip in the Arctic archipelago.
A district and appeals court had both freed him, ruling that the ban on flights over Norwegian territory -- and in the EU -- that was imposed on Russian nationals and entities did not apply to drones.
Following these acquittals, several other cases were dropped against Russians suspected of having flown drones over Norway.
The country's highest court, the Supreme Court, on Friday came to a different conclusion, finding that the term "aircraft" used in the EU sanctions document covered drones.
Norway is not a member of the EU but aligns itself with many of its decisions.
The Supreme Court said the district court could possibly review the case in light of other arguments presented by Yakunin's defence team, to see if he could still be cleared.
Yakunin's lawyers had argued that the 48-year-old businessman also held British citizenship and that his ties were primarily outside Russia, which would have made him exempt from charges, and that the rules were not sufficiently clear.
Yakunin's father Vladimir Yakunin is the former head of the Russian Railways and is sometimes described as a confidant of Putin.
Norway, which became Europe's biggest gas supplier following the war in Ukraine, has tightened security around sensitive sites, including energy installations, following the sabotage of the Nord Stream pipeline in the Baltic Sea.