BERLIN (AP) — Germany's highest court says an extra tax on nuclear fuel is unconstitutional, paving the way for power companies to claim back more than 6 billion euros ($6.75 billion) paid between 2011 through 2016.

The Federal Constitutional Court ruled Wednesday in favor of energy companies E.ON, RWE and EnBW, which argued they only agreed to pay the tax in return for being granted longer lifespans for their nuclear plants.

That changed after the 2011 Fukushima nuclear disaster, which prompted a U-turn in Chancellor Angela Merkel's pro-nuclear policies. Germany ordered nuclear power phased out by the end of 2022.

The tax required companies to pay 145 euros per gram of nuclear fuel each time they change a fuel rod. The companies argued this gave them a competitive disadvantage to other energy producers.