AUGUSTA — The owners of the Edwards Dam have formally appealed a federal decision to tear down the 160-year-old structure.

Lawyers for Edwards Manufacturing Co. on Monday requested a rehearing on the issue before the Federal Energy Regulatory Commission.

The agency voted 2-1 in November not to reissue an operating license to Edwards Manufacturing. It also ordered the company to pick up the tab, an estimated $6.4 million, for removing the 917-foot dam on the Kennebec.

The decision marked the first time federal regulators had ordered the removal of a dam when a licensee wanted to continue operating it.

On Monday, lawyers for Edwards Manufacturing said the agency’s ruling was unconstitutional and unfair.

“The orderly and reasoned assessment of the project proposal … has gone seriously awry,” said Donald Clarke, a Washington lawyer who represents the company. He said the ruling ignored “a cornerstone of … legislative history — that a licensee’s investment in a project was secure.”

Clarke also accused the agency of putting its desire to restore fish species to the Kennebec above other factors, without balancing the needs of the dam’s owners and people who own property in the area.

Removal of the 3.5-megawatt dam would allow salmon, shad and other fish to return to 17 more miles of the river that have been blocked off for generations, a move that has been applauded by environmentalists.

If FERC affirms the decision, the company has said it will challenge the decision in federal court.

The FERC order directed Edwards Manufacturing to file a removal plan within a year. The company’s request for a rehearing before the agency asks that a stay be granted pending the outcome of the hearing.

Gov. Angus King has said the state is willing to help mediate the conflict, but does not want to pay for the dam removal.