The Supreme Court has backed a multibillion-dollar oil railroad expansion in Utah in a ruling that scales back a key environmental law and could speed development projects around the country.

WASHINGTON — The Supreme Court backed a multibillion-dollar oil railroad expansion proposal in Utah on Thursday in a ruling that scales back the use of a key environmental law and could accelerate development projects around the country.

The U.S. Supreme Court dealt a setback to environmentalists on Thursday by allowing federal agencies to limit the scope of their reviews of the environmental impact of projects they regulate, as the justices bolstered a Utah railway project intended to transport crude oil.