PLEASANT POINT – Developers want to ship liquefied natural gas to needy customers in southern Maine and New England. Opponents want to block those shipments – and they may have found a barricade: an appeal process through the Interior Board of Indian Appeals and, if not there, the federal courts.

In May, the Passamaquoddy Tribe and its partner, Quoddy Bay LLC of Oklahoma City, Okla., signed a lease agreement that allowed the company to move forward with plans to build a $200 million LNG facility at Split Rock near Route 190.

Opponents, however, consulted Bar Harbor attorney Lynne A. Williams about the group’s window of opportunity to file an appeal, which they believed to be 30 days from the Bureau of Indian Affairs’ approval of the lease on June 1. Williams and an official at the Interior Board of Indian Appeals said the group could press the matter legally. Now Williams must decide whether to appeal the lease approval to the Interior Board of Indian Appeals or to take the opponents’ case directly to federal court.

Williams’ clients include Passamaquoddy tribal members Vera Francis, David Moses Bridges, Mary Bassett, Alice C. Tomah and Deanna Francis.

Williams, who was conferring with a Vermont law school professor familiar with this area of federal law, said she believes the 30-day window began when Quoddy Bay went public with the Bureau of Indian Affairs approval.

“We know we can appeal administratively [with the IBIA]. What we’re looking into is whether we must appeal administratively before going to federal court,” Williams said Tuesday.

In the meantime, Williams filed an objection to the lease agreement with the trust division of the Bureau of Indian Affairs, asking for it to investigate details of the proposed lease, aspects of which, she said, had been “hidden from scrutiny.”

In the July 6 letter, Williams based her client’s objections to the lease agreement on several procedural grounds including a “lack of transparency” because the governing tribal council at Pleasant Point was not allowed to see the lease until an hour before they voted on it. “And once the vote was over,” Williams said in her letter, “even those copies were taken back by the Quoddy Bay representative.”

She also objected to language in the lease agreement that says Quoddy Bay won’t have to pay property taxes. “While property taxes on an undeveloped parcel in this locale might be minimal, property taxes on the proposed LNG facility would no doubt run into millions over the lifetime of the property. The taxes might, in fact, total more than the lease fee itself.”

The company has agreed to pay the tribe an annual lease fee of anywhere from $6 million to $12 million depending upon the amount of LNG that flows through the system.

The plan calls for construction of a half-mile-long pier where LNG ships would dock. From there, the supercooled natural gas would be transformed back into gas and pumped in feeder lines to the Maritimes and Northeast Pipeline that runs from Nova Scotia to Boston.

Two tankers could dock at the same time if weather became a factor. Storage tanks could be built later if necessary.