Attorney General Tim Fox this week joined Montana to a lawsuit challenging the state of Washington and its denied expansion of a Longview coal port, suggesting the decision had no basis in law.

The joint amicus brief, filed in U.S. District Court in Tacoma, includes the attorney generals from the states of Montana, Wyoming, Kansas, Nebraska, Utah and South Dakota.

Last year, the Department of Ecology in Washington denied the environmental permits necessary for the expansion of the Millennium Bulk Terminal based in Longview, saying it would cause “significant and unavoidable harm” to the environment.

The project, proposed by Utah-based Lighthouse Resources, would increase the port's capacity and allow larger shipments of coal from the Powder River Basin in Montana and Wyoming to markets in Asia.

“Politicians in Washington state have again demonstrated their willingness to hold coal states hostage,” Fox said in a statement. “Gov. Inslee has made his ideological opposition to coal abundantly clear over the years, proving pro-coal projects will never get a fair shake by his administration. I’m working to ensure hardworking Montanans are treated fairly under the law.”

The suit was initially brought in January by Lighthouse Resources, the parent company behind the $680 million export proposal at the Millennium terminal at Longview.

At full build-out, the terminal could export 44 million metric tons of coal. Montana mined 32 million metric tons last year and claims nearly 25 percent of the world's recoverable coal reserves, according to Fox.

In the amicus brief, the states contend that Washington's denial of the expansion permits violated multiple federal laws. The brief includes the support of the National Mining Association and the American Fuel and Petrochemical Manufacturers, among others.

But the state of Washington argues that granting relief to Lighthouse and the states enjoined in the suit, including Montana, would interfere with its sovereign rights and remove its ability to manage its aquatic lands.

The state's supporters include the Sierra Club and the Washington Environmental Council. While the Montana Environmental Information Center isn't involved in the suit, it supports Washington's right to manage its own environment.

“If Fox wins and I'm Washington state, I'd send Montana the bill,” Anne Hedges, deputy director of MEIC, said Thursday. “They have the right to protect their economy. Climate change is expensive, their fisheries are valuable and they're trying to do their part to protect themselves from an unnecessary harm.”

The proposed expansion of the Millennium port isn't widely popular in Missoula and other Montana communities. Nearly 100 people gathered from across western Montana in Missoula in 2016 to weigh in on the environmental impact statement for the Longview port before the state of Washington denied the permit.

Hedges urged Fox to promote the future of energy, not the past.

“He needs to stop looking in the rear-view mirror and start looking forward to what we can do to build our economy,” she said. “He's fighting for a past nobody is interested in, and a coal economy that's in steep decline. There are cheaper, safer and better options.”

Fox said the federal case is currently in its early stages. If the case moves forward, the states will file additional briefs, expounding on the legal violations by the state of Washington.