BANGOR – A Superior Court justice on Thursday paved the way for a 224,000-square-foot Wal-Mart Supercenter off Stillwater Avenue, ordering the city’s planning board to reverse its April decision and approve the development.

Justice Jeffrey Hjelm in a written decision filed Thursday in Penobscot County Superior Court ruled that the city ordinance on which the planning board based its 3-2 denial was “unconstitutional and therefore unenforceable.”

The ruling comes just six weeks after The Widewaters Group, the project’s New York-based developer, sued the city contending that its planning board overstepped its authority when it denied the project, which would place the Supercenter – roughly 10 times the size of neighboring Circuit City – in a hayfield just south of the Penjajawoc Marsh.

In rejecting the plan, the board’s majority cited a vague city ordinance that allows them to consider the development’s “effect on the scenic or natural beauty of the area or … rare and irreplaceable natural areas,” namely the nearby Penjajawoc, home to a number of bird species on the state’s endangered or threatened lists.

The wetland became the focus of a heated debate in recent months, with opponents decrying the plan to place the giant store near a portion of the environmentally sensitive 350-acre area.

Thursday’s ruling marked the first major victory for Wal-Mart’s Bangor project, which has been bogged down for months in state and city regulatory boards.

Widewaters attorneys reached Thursday praised the justice’s decision, adding that the developer is expected to issue a statement today about future plans for the 27.4-acre parcel, purchased last year for $2.3 million.

But the future of the land was not set in stone by Hjelm’s decision, which could be appealed by a local opposition group, Bangor Area Citizens Organized for Responsible Development.

In an earlier ruling, Hjelm allowed the group to intervene in the case. The status gives the group the right to appeal the decision to the Maine Supreme Judicial Court.

BACORD spokeswoman Valerie Carter said Thursday that there was a “good chance” the group would appeal, but it would review Hjelm’s decision and consult its attorney as they “very strongly consider” the option.

Carter, dismayed by the ruling, said more is at stake than a giant Wal-Mart breaking ground near the Bangor Mall.

“The well-being of our community is at stake. Our independence and integrity as a community is at stake,” she said. “If communities aren’t given the tools to deal with changes that will affect them for decades, it points out that we need to take another look at our policies at the city and state level.”

City Solicitor Norm Heitmann said he was disappointed in Hjelm’s finding that the city ordinance was unconstitutional. Heitmann said that in coming days he would advise the City Council of its options, including an appeal or a retraction of the unconstitutional ordinance.

Both BACORD and the city have 30 days in which to appeal.

Also in Thursday’s ruling, Hjelm dismissed Widewaters’ claim that planning board member Frederick Costlow had demonstrated bias against the project when he sent a letter asking the City Council to extend the protected area around the wetland.

In one of the project’s first major setbacks, Maine Department of Environmental Protection officials promised to reject an initial plan that placed the development within the 250-foot buffer recommended by state wildlife officials.

Widewaters amended the plan, moving the project away from the marsh but leaving a small section of a detention pond within the buffer.

The proposed Bangor project – some 5 acres of building space and 13 acres of parking – would replace the existing Wal-Mart, which opened on Springer Drive in 1992.

The Arkansas-based retail giant also recently announced plans for a 155,000-square-foot Supercenter in neighboring Brewer.

Wal-Mart spokesman Keith Morris, reached Thursday, said he was pleased with Hjelm’s decision, and the company remained committed to building in both Bangor and Brewer.