Kansai Electric had intended the reactors in Fukui to be among the first in the country to be returned to service after the introduction of the new rules more than two years ago. But in his ruling on Tuesday, the judge, Hideaki Higuchi, challenged the adequacy of the standards, which cover things like plants’ resistance to earthquakes and tsunamis, the triggers for the Fukushima disaster.

“There is little rational basis for saying that an earthquake with a magnitude that exceeds the safety standard will not occur,” said Judge Higuchi, 62. “It is an optimistic view.”

The reactors had been widely expected to return to service by the end of the year. While Kansai Electric said it would appeal, experts said its plans could be delayed by months or even years.

It was the second time Judge Higuchi had issued an order forbidding a nuclear plant in Fukui to operate, and he remains the only judge in Japan to have ruled against a utility over nuclear restarts since Fukushima. He became a hero among antinuclear activists in May when he ruled that two reactors at another Kansai Electric facility, the Oi nuclear plant, must remain switched off because the utility had not shown that they could be operated safely.

Judge Higuchi’s decision on Tuesday was potentially more significant because it directly challenged the new safety standards set out by the Nuclear Regulation Authority. It was his first ruling against a plant that had been certified as safe under the new regulations; the Oi power station had yet to undergo a safety review.

The injunction was requested by a group of nine residents of Fukui and surrounding prefectures.

“This ruling is a historic step toward abolishing nuclear power, and the government and power company should respect it,” a lawyer for the group told NHK, Japan’s national broadcaster.

Judge Higuchi’s critics say he lacks the technical expertise to reach conclusions about nuclear safety.