The latest challenge to the proposed Southwest Corridor light-rail line is a federal lawsuit filed by residents and the owner of Claremont Apartments in Minnetonka, which is adjacent to an area of woods and trails. Portions of the line would come as close as 90 feet to the apartments.

The suit claims that the Metropolitan Council, which would build the line (also called the Green Line Extension), violated federal environmental laws and did not properly follow Minnesota’s municipal-consent process because it sought approval before an added environmental review was issued. (A similar lawsuit regarding the Kenilworth Corridor was filed last year by the Lakes and Parks Alliance of Minneapolis.)

The case is complex. But the ruling will have impact on the progress — and cost — of the line, since a delay in construction would add expense to the current estimate of about $1.6 billion.

The two lawsuits are significant. But it’s important to remember that previous light-rail projects faced hurdles, too. The Central Corridor (the Green Line) had high-profile disputes with the University of Minnesota and Minnesota Public Radio, for instance, but those were resolved, and ridership figures confirm the line is now an unquestioned success.

Indeed, a more ominous obstacle for Southwest may loom to the east, at the State Capitol, where Republican resistance in the Legislature might make building extensions of both the Green and Blue lines nearly financially impossible.

Those legislators should seize upon a truly unique opportunity for the metro area and the state. The federal government may pay up to half of the project’s cost, and the line is increasingly backed by the Obama administration, which budgeted $150 million for Southwest as a first installment of the federal funding process. Additionally, the Federal Transit Administration recently upgraded Southwest’s ranking to “medium-high” from “medium,” signaling that federal funds could come if state and local funding is secured.

Businesses, workers and the state’s economy would benefit from a better link between downtown Minneapolis and the job-rich southwestern suburbs. Legislative leaders should not let ideological rigidity squelch this pro-growth transit opportunity.