The ruling will not have an immediate impact as Norway's minority government decided not to issue any mining licences this year, after making a deal with a small party to be able to stay in power.

But it may in future open up the seabed in the Scandinavian country's waters, which is controversial for its potential impact on vulnerable marine ecosystems.

Besides the risk of chemical leaks, environmentalists argue it poses a threat to the habitats of sea species as well as from from potential noise and light pollution from the machinery used.

Last November the Norwegian branch of WWF took the government to court, accusing it of failing to carry out sufficient impact studies.

"We disagree with this part of the courts (sic) reasoning and will carefully review its reasoning to determine whether to appeal," said WWF-Norway CEO Karoline Andaur.

Norway, western Europe's biggest oil and gas producer, had planned to become one of the world's first countries to start handing out rights to tens of thousands of square kilometres (miles) of seabed.

Copper, cobalt, zinc and rare earths are believd to be present in its continental shelf. All are essential for production of batteries, wind turbines, computers and mobile phones.

The government had argued that deep-sea mining would allow it to reduce reliance on China for minerals essential to the transition to a lower-carbon economy.

In December the small Socialist Left Party said it had blocked the allocation of licences in return for supporting the minority Labour government's 2025 budget.