A Seavey Island in the Piscataqua River, home to the Portsmouth Naval Shipyard in 2001. Seen from the east, Kittery is to the right and Portsmouth in the upper left. Gregory Rec/Portland Press Herald file

A New Hampshire legislator has fired the latest round in an on-again, off-again border dispute between Maine and New Hampshire over the Portsmouth Naval Shipyard.

Republican Rep. Joseph Barton, a freshman lawmaker, is the prime sponsor of legislation urging Congress to find that the Piscataqua River and Portsmouth Harbor are within New Hampshire and asking President Donald Trump to designate the duty stations of Portsmouth Naval Shipyard personnel as Portsmouth, N.H., sites.

Congress would have to redraw the boundaries, but Trump can re-assign the duty stations, Barton said.

The tax status of shipyard employees is a big reason for the legislation, he said. New Hampshire does not have a state income tax, and residents of the Granite State who work at the shipyard pay Maine taxes. Shifting the borders to bring the shipyard into New Hampshire would shield New Hampshire residents from Maine income taxes.

“We won’t get more tax revenue,” Barton, who worked as an engineer at the shipyard, said in an interview Thursday. “The citizens will get more tax relief.”

Some Maine income tax revenue would disappear if the more than 3,100 New Hampshire residents who work at the Portsmouth Naval Shipyard no longer have state taxes withheld. It wasn’t immediately clear how much revenue Maine would lose; a spokeswoman for the state Department of Administrative and Financial Services said taxpayer confidentiality bars disclosure of information.

Kittery Town Manager Kendra Amaral said New Hampshire would inherit traffic problems if it takes possession of the Naval Station, which has two land-based access points, both of which run through Kittery.

If New Hampshire wants the shipyard it will need to build bridges from Portsmouth to the Naval Station island, “so they can assume all of the traffic congestion and infrastructure impacts Kittery, Maine, shoulders as the host of the (shipyard),” Amaral said.

The issue of who has jurisdiction is not new. The U.S. Supreme Court unanimously ruled on a border dispute in Maine’s favor in 2001, dismissing New Hampshire’s claim to the shipyard. The court denied a New Hampshire request to reconsider. It said the boundary between the states is the middle of the Piscataqua River.

More than half of the shipyard’s nearly 8,000 employees are Mainers, according to the Seacoast Shipyard Association, an advocacy organization. And 56% of the Portsmouth shipyard’s $716.2 million payroll is for Mainers and 36% is paid to New Hampshire residents. The remainder live in Massachusetts and other states.

Its total economic impact in 2023, including purchased goods and services, maintenance and military construction, was more than $1.5 billion.

Barton’s resolution says jurisdiction and control over the Piscataqua River “is and always has been entirely” within New Hampshire’s Rockingham County and “complete dominion and ownership of the tidal waters and submerged lands” of the river, including Portsmouth Harbor, are part of the state.

“This is the boundary. This is where it is,” he said.

The resolution has been the subject of a public hearing and must be voted on by the House and Senate and signed by Gov. Kelly Ayotte. Her office did not immediately respond to an email asking if she supports the measure.