The Kanazawa District Court in March 2006 ordered Hokuriku Electric Power Co. to shut down the No. 2 reactor at its Shika nuclear power station in Ishikawa Prefecture — the nation's second largest power reactor. The unprecedented ruling said the reactor lacked sufficient earthquake resistance and could expose residents to radiation in the event of a major quake. The lawsuit was filed in May 2005 by 128 people from 16 prefectures. The Nagoya High Court's Kanazawa branch overturned the ruling March 18, saying the reactor's resistance to earthquakes was adequate.

Still, the power industry should not lower its guard against quakes. The conditions under consideration at the appellate trial differed from those of the first trial. The design of the Shika No. 2 reactor was based on 1981 quake-resistance guidelines, the defects of which had been exposed. The lower court ruling apparently prompted the Nuclear Safety Commission to revise the guidelines. It came up with new, stricter guidelines in September 2006. Based on the new guidelines, Hokuriku Electric Power reinforced the quake resistance of the reactor.

The high court ruling said that since the company utilized the latest knowledge in assessing geological faults, its assumption of possible maximum seismic tremors is appropriate. Although the plaintiffs said the maximum magnitude of quakes caused by unknown fault activity should be assumed to be 7.3, the ruling said the company's assumption of magnitude 6.8 was appropriate.