The U.S. Supreme Court appeared open to diminishing the scope of how federal agencies consider environmental impacts Tuesday in a case centered on a proposed oil railway in northeastern Utah.

The Supreme Court seemed to favor a Utah oil railroad expansion in arguments on Tuesday, but appeared more skeptical of putting strict new limits on a key national environmental law. The justices were weighing a multibillion-dollar project that could quadruple oil production in the remote area of sandstone and sagebrush.

Justices on the U.S. Supreme Court on Tuesday appeared generally willing to strike a blow against a key federal environmental law in a case brought by Coloradans against a controversial Utah oil-train project — but they struggled to reach a consensus on exactly how to define the new limits they might impose on the law.