Opponents of the proposed Nantucket Sound wind farm in Massachusetts appealed the dismissal of a federal lawsuit challenging an energy contract for the project.

The lawsuit, the latest in a string of failed challenges to the project, argued that state regulators’ approval of an above-market contract to sell power from the project to NStar violated two clauses of the U.S. Constitution: the Commerce Clause and the Supremacy Clause, according to the Cape Cod Times.

NStar delivers power to Cape Cod, Martha’s Vineyard and other parts of Massachusetts.

The suit was filed against Cape Wind, state officials and NStar by the town of Barnstable, the Alliance to Protect Nantucket Sound and several individuals and businesses.

U.S. District Judge Richard Stearns found on May 2 that the plaintiffs, who had sued officials at the state Department of Public Utilities and the state Department of Energy Resources, were barred from doing so under the 11th Amendment to the Constitution, which restricts lawsuits in federal court against a sovereign state for past actions.

In addition, he found that even if the lawsuit had passed the 11th Amendment test, it still would have lost on the merits.

On Monday, Hyannis Marina Inc., Jamie Regan and the Alliance to Protect Nantucket Sound filed notice that it was appealing the dismissal. The town of Barnstable filed a separate notice of appeal.

There have been no other filings related to the appeal so far, said lawyer Matthew Price, who represents the group that includes the Alliance to Protect Nantucket Sound.

“The project opponents have lost 26 lawsuits and appeals against Cape Wind and seem determined to lose another one,” Cape Wind spokesman Mark Rodgers told the paper.

Cape Wind first proposed a wind farm in the sound in 2001. Company officials have been gathering financial support for the project, which is expected to cost more than $2.6 billion, and said earlier this year that they expect to begin onshore cable construction by the end of the year and ocean-based construction by 2015