A state Land Court judge ruled Tuesday that the Oak Bluffs planning board overstepped its authority when it denied the Martha’s Vineyard Regional High School’s application for an artificial turf field on the basis of ground water protection.

In a 13-page ruling, Judge Kevin Smith allowed the school’s request for a summary judgment, ordering the planning board and the school to collaborate on a plan to move forward within the next 30 days. The long-awaited decision lays out the limitations of the planning board’s power, a major question that has been outstanding since the board denied the project in 2022.

The planning board denied the school’s application after several contentious hearings, saying materials from the synthetic field could hurt the area’s aquifer. The school claimed it was immune from the regulations because of the Dover Amendment, a state law that bars zoning regulations from stopping the use of land or buildings for educational and religious purposes.

There are some exceptions to the Dover Amendment, but in his decision, Judge Smith said the town can only impose dimensional restrictions.

“The board acted beyond its authority when it imposed water protection regulations of the [Water Resources Protection Overlay District] on the artificial turf field project,” he wrote. “I recognize that the protection of groundwater is of critical importance to any municipality, particularly when that municipality is on an island in the Atlantic Ocean. But I am constrained by the language of the Dover Amendment and the cases that have construed it.”

The school and the planning board are required to tell the court whether there are any other issues that need to be tried and whether further discovery is needed. After the joint report is filed, the court will hold a further conference on the matter.

The judge’s decision comes almost two months after he heard the school and planning board argue their cases on whether the case should go to a full trial. Much of Tuesday’s ruling dealt with the definition of “open space.”

Oak Bluffs’ denial hinged on water protection regulations falling under the open space exemption allowed in the Dover Amendment.

Aside from open space, which is left undefined in the state zoning act, the exemptions under the Dover Amendment all have to do with dimensional requirements, leading the judge to infer that open space was another dimensional limitation.

“I am not persuaded that the inclusion of the term ‘open space’ in the Dover Amendment was intended to be broadly construed to open the door for an educational use to be regulated, and even stopped, by water protection regulations, no matter how important the protection of water resources may be,” Judge Smith wrote.

The regional high school committee is scheduled to meet Monday to talk about the appeal and the potential of re-hiring attorney Brian Winner. Mr. Winner had been handling the case for the school.

Schools superintendent Richard (Richie) Smith said there is still much work to do on overhauling the school’s fields.

“This has been a very long, ongoing process,” he said. “We’d like to get a full understanding of a judge’s decision before we offer a full opinion.”

Paying for Mr. Winner’s services will also likely be discussed at the meeting. The school committee previously vowed to not use any of this year’s budget on the appeal, though it had taken some private donations to cover the attorney’s costs.

Ewell Hopkins, the chair of the Oak Bluffs planning board, said the decision lays out authority of the planning board, but it doesn’t give the school the go-ahead to start building a field.

“He has not said ‘Go forth and prosper,’” Mr. Hopkins said. “He has defined the authority under zoning bylaws.”

Mr. Hopkins said he saw the decision late Tuesday afternoon, but had not been able to discuss it with the rest of the planning board. A meeting between school and Oak Bluffs officials has not yet been scheduled.