A federal judge ruled Tuesday that the Tennessee Valley Authority (TVA) must install $1 billion in pollution controls to reduce air pollution crossing into North Carolina. The landmark ruling sets a precedent for other states to take legal action over interstate air pollution.

North Carolina filed suit against TVA three years ago, alleging that the air pollution generated from its coal-fired power plants was a public nuisance adversely affecting the health of North Carolinians. Judge Lacy Thornburg agreed with North Carolina in his decision, ordering TVA to install scrubbers and pollution control equipment in the four coal-fired power plants within a 100-mile radius of North Carolina’s borders.

The ruling opens the door for more litigation between states over air pollution, which may lead to federal action on coal plant emissions nationwide.