Legal action is being taken against the German state of Hesse by RWE, an energy company, after it was ordered to close a nuclear power plant for three months.
The BBC reports the order came soon after an earthquake and tsunami caused a nuclear emergency in Japan on 11 March.
RWE said the reactors were safe so the state had no reason to disrupt its energy generating activities.
In a statement, the company also said the state of Hesse had no legal authority to order it to close the Biblis nuclear plant.
The plant was shut down as part of an industry-wide moratorium after German Chancellor Angela Merkel ordered additional safety checks on Germany's seven oldest nuclear power plants following the crisis in Japan.