WASHINGTON – The U.S. Supreme Court once again heard oral arguments Monday in the 260-year-old border dispute between Maine and New Hampshire.

The issue and New Hampshire’s lawsuit could be resolved quickly if the court rules in favor of Maine’s motion to dismiss. If the justices reject the motion, however, the case could be placed in the hands of a special magistrate, which could lead to a full trial and take years to resolve.

Maine considers the border that separates the two states to be in the middle of the Piscataqua River. New Hampshire, however, argues that the boundary line should be drawn along Maine’s shoreline. At stake is the Portsmouth Naval Shipyard, located in the middle of the river on Seavy Island.

About 4,000 people are employed at the shipyard including almost 1,500 New Hampshire residents who now pay about $5 million in Maine state income taxes on their shipyard salaries.

Paul Stern, deputy attorney general and chief of the state litigation division who presented Maine’s case, said after making his oral argument before the Supreme Court that it is impossible to predict the final outcome from the reactions of the justices. “They asked the right questions, and I hope we gave them the right answers,” Stern said.

Leslie Ludtke, special counsel for the state of New Hampshire, said this case “is about boundaries, not money.”

“Maine has tried to make this a case about the shipyard instead of about the borders of the state,” she said. New Hampshire’s sovereign interests are at stake, specifically its right to control Portsmouth Harbor, she said.

“New Hampshire doesn’t get any money if the state wins the case, because residents don’t pay income taxes there,” Ludtke said.

However, if Maine were to lose the case and the border were shifted so that the shipyard became part of New Hampshire, Maine would lose the income tax revenue generated by the people who work there.

The conflict between the states goes back to 1740, when King George II declared the border to be “in the middle of the river.” In 1976, the U.S. Supreme Court accepted an agreement between the two states setting the border in the middle of the river.

Last year New Hampshire filed a suit asking that the border be redrawn to follow the Maine coastline which would place Seavy Island and the Portsmouth Naval Shipyard within New Hampshire’s borders.

In its motion to dismiss the case, Maine argued that the Supreme Court settled the issue in 1976 and therefore should dismiss New Hampshire’s claim.

“New Hampshire had the chance to raise issues and questions in 1976, and their failure to do so precludes them from doing so now,” Stern said.

But Ludtke argued that New Hampshire has conducted extensive research since 1976 and discovered historical documents that support the state’s claim. “If the attorneys general had known back then what we know now, they would not have signed the agreement,” she said.

Stern, however, dismissed Ludtke’s claims after the hearing. “From the evidence we have seen, New Hampshire’s historical documents lead to a dead end,” he said.

The justices seemed annoyed with Ludtke’s assertion during oral arguments that the term “middle of the river” is ambiguous. “If it was ambiguous, New Hampshire shouldn’t have signed the agreement [in 1976],” Justice Antonin Scalia said.

Justice Stephen Breyer strongly questioned Ludtke’s argument that parts of the 1740 decree are valid but others are irrelevant.

“Is there anybody other than a totally irrational, illogical person that could defend that position?” Breyer exclaimed at one point.

Justice David Souter, a former New Hampshire attorney general who helped litigate the state’s Supreme Court case in 1976-77, has recused himself from consideration of the case this time around.

The federal government supports Maine’s position and the U.S. Solicitor General’s Office has filed a brief which says the Supreme Court’s earlier decision should stand.

Members of the Maine congressional delegation said they are watching closely how the case proceeds. “My wife was born in the shipyard’s hospital,” said Rep. John Baldacci, “so we are very interested in what’s happening.”

Baldacci said he does not believe New Hampshire has a strong case and called it “unfortunate it’s taking up the court’s time.”

Sen. Olympia Snowe said New Hampshire’s own state maps place the shipyard in Maine, as does the U.S. Census Bureau.

“New Hampshire’s lawsuit is yet another transparent effort to infringe upon the state of Maine’s right to tax those who are employed within its clearly defined borders,” she said in a statement.

Rep. Tom Allen said he is sure that New Hampshire will accept the court’s decision. Of course, he said, “you can’t make everybody happy.” He added that it was time the case was decided so people could “get on with the rest of their lives.”

Sen. Susan Collins said, “I’m optimistic that the Supreme Court will decide once and for all that that is the case.”

The court is expected to decide on Maine’s motion to dismiss the New Hampshire lawsuit by the end of June.