Public access to a popular sand beach in Harpswell will no longer be permitted if a decision by Maine’s highest court stands.

The Maine Supreme Judicial Court on Tuesday unanimously vacated a lower court judgment concerning a long-running dispute over access to Cedar Beach on Bailey Island. It remanded the case to Superior Court, which had previously ruled that the public had established the right to use a private road to access the beach. The supreme court ruling was published on the court’s website.

An attorney for Bailey Island residents and the nonprofit Cedar Beach/Cedar Island Supporters Inc., representing more than 300 people seeking access to the beach, said the plaintiffs now have 15 calendar days to ask the court to reconsider.

Attorney David W. Bertoni said he would have to demonstrate that the justices made errors in their ruling for such an appeal to succeed. He declined to elaborate on what those mistakes might be.

“Obviously, this will be an uphill battle, but we are not prepared to give up yet,” Bertoni said.

In September 2014, Bertoni’s clients celebrated when a Superior Court judge ruled that the public had access rights to Cedar Beach Road, a private road leading to the beach.

Superior Court Justice Nancy Mills, following a three-day bench trial, wrote a 73-page decision granting the public a prescriptive easement to Cedar Beach Road – which provides the only land access to the beach. Prescriptive easements recognize that the public has effectively earned the right to use private property after having uninterrupted access for a long period of time.

The Superior Court decision was appealed by the owner of Cedar Beach Road – a real estate corporation called Gables Real Estate LLC, according to court documents. Betsy Atkins, who owns a home near the beach but lives in Florida most of the year, was identified in the 2014 court decision as the owner of Gables Real Estate LLC.

The sides argued their case before the Maine Supreme Judicial Court in November and the court issued its ruling Tuesday morning.

“Our client is pleased that the Supreme Court has upheld private property rights and unanimously ruled that Cedar Beach Road remains a private road,” Christian Chandler, a Portland-based attorney for Gables Real Estate, said in a statement. “The Court found that the previous owners of the road had taken adequate steps to keep the road private and that the public does not have a right to access the shore from Cedar Beach Road.”

“We are optimistic now that all parties have been given a fair opportunity to be heard in Court, that the public will respect the Court’s decision and the private property rights of the owners of Cedar Beach Road,” the statement said.

Cedar Beach had been used by the public for decades until 2011, when the access road was barricaded by former owners Charles and Sally Abrahamson. After multiple attempts at negotiating public access failed, residents and the nonprofit filed the lawsuit.

Atkins has since purchased the Abrahamson property and road, and has also denied the public access. The public is allowed to use the beach, but the only way to reach it now is by boat.

The public’s reaction Tuesday on a Facebook page called “Save Cedar Beach Maine” was strong.

“No words. Just sadness and I don’t even live on the island. I can’t believe this person has a heart or soul to take away something that belongs to the island and its people,” wrote Donna Brown, who has vacationed on Bailey Island for seven years.

“Disappointing isn’t the right word. Makes me sick to think this woman can move to Bailey Island and just take over our beach! I really feel like it is home,” wrote Wendy Johnson Lefavor.

“Sad news for sure. Grew up going to that beach all summer,” Sue Stevenson said.

And Liza Watts added: “Heartbreaking. My three-year-old son will not be able to create any memories of a beach used by his great-great-grandparents, great grandmother, grandmother, aunts, uncles, cousins and his mom. Shame.”

Bertoni said he remains hopeful that the court will reconsider its decision or that Atkins might be willing to negotiate an agreement that would allow access. He described his clients as ordinary people who for generations have been able to use the road to get to Cedar Beach.

But Bertoni said the coast of Maine has “become a magnet for the wealthy,” and acquisition of oceanfront land has eroded the access rights of working families.

“I grew up in a poor family in Connecticut and the only thing we had that gave us great joy was being able to go to the beach,” Bertoni said.