Credit: Dreamstime | TNS

South Portland’s ordinance prohibiting bulk loading of crude oil onto tankers is in the hands of a panel of federal judges in Boston.

A federal judge already ruled that South Portland’s “clear skies” ordinance passed constitutional muster, but Portland Pipe Line Corp. took the case to the 1st U.S. Circuit Court of Appeals, which heard arguments last week.

The ordinance blocked the company from reversing the flow of its 236-mile underground pipeline.

The pipeline has carried foreign crude from harbor terminals in South Portland to Canadian refiners for decades. But the company wants to reverse the flow to bring oil from Canada.

Critics say they don’t want the coastline to be industrialized. They also say the tar sands oil is a dirty and destructive form of fuel.