A court decision issued Tuesday brings new uncertainty to whether nuclear materials on a Gloucester County site will be shipped to Utah or kept in place.

The ruling from a federal appeals court in Washington sent the question back to the federal Nuclear Regulatory Commission.

The commission ruled in 2011 that New Jersey's Department of Environmental Protection would be in charge of the cleanup at the site in Newfield where Shieldalloy Metallurgical Corp. made metal alloys from 1955 until 1998. The process had a radioactive by-product.

What to do with the leftover material has been the subject of litigation and regulatory battles for a decade.

The DEP has stricter regulations for handling of nuclear slag than the federal government does. The NRC agreed that the state rules should apply.

The state is seeking to have the material shipped to Utah for disposal. That option would be more costly for Shieldalloy, a subsidiary of Wayne-based Metallurg Holdings Inc., and the company says it is more dangerous.

The latest ruling does not settle the question.

Senior Circuit Judge Stephen F. Williams wrote in the majority opinion that the NRC needed to "explain itself in a way that rationally addresses the concerns," and found its decision to hand the matter off to the state to be "arbitrary and capricious," but the NRC could still decide to give authority to New Jersey regulators.

In an opinion that partially concurred and partially dissented, Judge Judith W. Rogers found that the NRC's decision was not arbitrary.