A bitter legal battle over the fate of the $2 billion Southwest light-rail line ended Monday after a federal appeals court ordered a longstanding lawsuit challenging the project to be dismissed.

In 2014, a group of residents called the Lakes and Parks Alliance (LPA) filed suit in federal court against the Metropolitan Council and the Federal Transit Administration (FTA) charging that the Southwest project violated federal and state environmental laws. Southwest is the largest public works project in state history.

The residents argued that the council improperly committed to a route for the line — specifically through the Chain of Lakes area in Minneapolis — before environmental reviews were complete.

In its opinion released Monday, the U.S. Court of Appeals for the Eighth Circuit said the district court that heard the original case lacked jurisdiction to hear the alliance's claim.

Construction of the 14.5-mile line, slated to link downtown Minneapolis to Eden Prairie, has already begun, with passenger service expected to begin in 2023. St. Louis Park, Minnetonka and Hopkins also are part of Southwest's route.

Met Council Chairwoman Nora Slawik said in a statement Monday she was pleased with the appeals court ruling.

"As we have contended over the last several years, this lawsuit was without legal support and should be dismissed," she said.

The lingering lawsuit had cast a cloud of uncertainty over the project, which is controversial among some who question its cost and its route — particularly through the Kenilworth corridor, a popular bike and pedestrian path in Minneapolis.

"We feel profoundly betrayed by the justice system," said Lakes and Parks Alliance spokeswoman Mary Pattock. "At no time did our case get considered on its merits — namely, our charge that the Met Council violated federal law by not seriously considering less environmentally damaging routes before committing prematurely to this one; they made their decision based on political considerations."

The federal government, which the council expects to contribute $929 million toward building the line, was dropped from the suit in 2015. The FTA requires an environmental review of big transit projects like Southwest, while state law calls for cities along the proposed route to approve the route, too.

U.S. District Judge John Tunheim ruled against the group last year, saying agreements with cities along the route amounted to "promises that can be broken." The group later appealed the decision.

The appeals court on Monday ordered the case returned to the lower court with instructions to dismiss it.

The court also wrote: "Because we hold that the LPA does not have a viable cause of action, we need not address the claim on the merits."

Pattock replied that the "result is that ordinary citizens now have no practical remedy to defend their rights under this federal law."

It was unclear Monday how much the case, which was filed nearly five years ago, cost the Met Council in legal fees. Slawik also said in her statement that "ongoing construction was not delayed by this lawsuit."

When asked if the alliance has any further legal remedy, Pattock said it did not.