Plans to bring Kansai Electric Power Co.’s Takahama No. 3 and 4 nuclear reactors back online were dealt a severe setback Tuesday when the Fukui District Court ordered that they not be restarted, citing safety concerns.

It marks the first time in Japan’s nearly half-century of commercial atomic power operations that a court has approved a provisional injunction against firing up reactors.

The decision comes despite the Nuclear Regulation Authority appraising the reactors against technical and safety criteria and clearing them for restart last November.