A superior court judge Monday handed a victory to the Martha’s Vineyard Airport Commission, ending a costly protracted legal battle with the Dukes County Commission over control of the Island’s only commercial airport.

In granting summary judgment, the Hon. Cornelius Moriarty 2nd ruled in favor of the airport commission on every point of the dispute, finding unequivocally that the state law that established the airport trumps the county charter.

“This case stands as another chapter in the long-running power struggle between the Martha’s Vineyard Airport Commission and the county commission for Dukes County over control of the Martha’s Vineyard Airport,” Judge Moriarty wrote in the 18-page decision.

The ruling says the county manager cannot sit on the airport commission as an ex-officio, non-voting member; the county treasurer cannot refuse to pay invoices authorized for payment by the airport commission; the treasurer cannot obtain privileged and confidential communications between the airport or release privileged communications to the public; and the county cannot expand or reduce the size of the airport commission.

Barring appeal by the county, the case is over.

As in past court battles, the case came down to a conflict between Chapter 34A, the state law that authorizes county government by charter, and Chapter 90, which established the airport commission. Central to the case are a set of grant assurances which the county signed in 2011 as a condition of receiving state and federal funds. In signing the grant assurances, the county, which appoints the airport commission, agreed not to take any action to interfere with the affairs of the airport without the approval of the Massachusetts Aeronautics Commission.

Judge Moriarty noted he had reached the same conclusion as two other superior court associate justices on three previous occasions.

“This court agrees with both justices that as a matter of statutory construction, when in conflict, the provisions of the charter, a broad enabling statute, must yield to the airport act, a narrowly tailored statute,” he wrote. “On the one hand, the county claims that the provisions of the charter trump the airport act. Yet on the other hand, it agrees that the grant assurances are a binding contract and it committed to the grant assurances being honored. It appears that the county seeks to run with the hare and hunt with the hounds. It may not do so. Here the county has forfeited its right to manage the airport through the execution of grant assurances and the acceptance of state and federal funds.”

The case has been full of twists and turns. The dispute stems to 2013 when the county treasurer began to question legal spending at the airport, refusing to pay certain legal bills without original invoices. The previous pattern had been for the airport to submit invoices with certain confidential information redacted. The treasurer contacted the airport attorneys directly, seeking to obtain original invoices.

“These actions set in motion the current flurry of legal punches and counter-punches,” Judge Moriarty wrote.

In April 2014 the airport filed a lawsuit in superior court to enjoin the treasurer from refusing to pay the invoices and from publicly disclosing unredacted copies of the airport legal bills.

The county commission then moved to appoint the county manager as an ex-officio, nonvoting member of the airport commission, which is permitted by statute. The airport amended its complaint to enjoin the county manager from serving on the commission, claiming such a move ran afoul of the grant assurances which prohibit any airport reorganization without approval of the state aeronautics board.

In August 2014, the Hon. Richard Chin, an associate justice of the superior court, ruled in favor of the airport by granting a preliminary injunction.

“Not to be outdone, on Sept. 24, 2014, the county voted to expand the size of the airport commission from seven to nine members,” Judge Moriarty wrote in the ruling this week.

One day later the administrator of the Massachusetts Aeronautics Division wrote to the county demanding an explanation.

More exchanges followed, and the airport again amended its complaint, seeking to prohibit any expansion of the airport board. Judge Chin again sided with the airport and the expansion was blocked.

In the ruling this week, Judge Moriarty said the airport commission is entitled to summary judgment because the facts of the case are not in dispute, and even in light most favorable to the county commission, the airport commission’s position is valid as a matter of law.

He was clear on matters involving county treasurer Noreen Mavro-Flanders’ refusal to pay invoices.

“Her refusal . . . violates the requirements of the grant assurances. It is undisputed that the [airport commission] is financially self-sufficient and that no county funds are expended for its operations. As such, the treasurer possesses no statutory oversight concerning these invoices,” the judge wrote.

He used similar reasoning in deciding whether county manager Martina Thornton may sit as an ex-officio member of the airport commission.

“This appointment clearly runs afoul of the promises made by the county in the grant assurances wherein it agreed ‘not to take any action to reorganize the airport commission,’” the judge wrote.

On the matter of expanding the airport board from seven to nine members, the county argued it had permission from state aeronautics officials to do so. The judge disagreed.

“I see nothing in the summary judgment record to suggest that the written approval of Aeronautics was obtained nor is there any record evidence to support the proposition that the requirement was waived,” he wrote.

Reached by telephone Tuesday, airport attorney David Mackey said he was pleased with the decision.

“We are happy with the result,” he said. “The judge’s decision is clear and speaks for itself.”

Leon Brathwaite, chairman of the county commission, could not immediately be reached for comment. But county commissioner John Alley, a former longtime airport commissioner who was ousted from the airport board by the county commission last year, said he was not surprised at the decision.

“I think it was a stunning and complete rejection of the county’s argument,” Mr. Alley said.