The definition of what wetlands are and when developers can build on them was the topic of a sharply divided U.S. Supreme Court decision released Monday.

The court, in a 5-4 vote, ruled that Michigan wetland regulators might have misinterpreted the federal Clean Water Act when they refused to let two Michigan property owners build on wetlands.

The court voided rulings against June Carabell and John Rapanos, who wanted to build on wetlands they owned near Lake St. Clair in Macomb County.

Carabell wanted to build condos on wetlands she owns about a mile from the lake, and Rapanos wanted to put a shopping mall on his property.

Instead of ruling in the property owners' favor, as they requested, justices said lower courts must reconsider whether or not ditches and drains near wetlands are waterways. The answer could determine if contractors are allowed to build on them.

Zoology and fisheries and wildlife Professor Thomas Burton said navigable waterways and adjacent water bodies are regulated, but the question of what is navigable is up for debate.

He said wetland protection and development dreams often clash, and this ruling is important to the nation, not just Michigan.

"The Supreme Court ruling has potential implications for the entire U.S.," he said. "It's been followed closely. If it would have been a straight ruling in favor of the state, everybody would have breathed a huge sigh of relief."

Steven Voice, president and owner of Voice Environmental Consulting Firm, which specializes in wetland and regulatory issues for developers, said one of the major points of contention is what exactly defines a wetland.

"I don't think they intend to regulate ditches," he said. "It's important to protect wetlands, and it's a good idea, but a lot of these ditches are establishing jurisdiction."

In the decision, Justice Antonin Scalia said the Army Corps of Engineers, which regulates wetlands, misinterpreted the term "waters of the United States."

"In applying the definition to 'ephemeral streams,' 'wet meadows,' storm sewers and culverts, … man-made drainage ditches, and dry arroyos in the middle of the desert, the Corps has stretched the term 'waters of the United States' beyond parody," he said.

Burton said that in the past, this case wouldn't be up for much debate in the Supreme Court.

"The judicial system is routinely in favor of the state," he said. "In the old Supreme Court, (the plaintiffs) didn't have a prayer."

Until the lower courts decide on the cases, everything's up in the air, Burton said.

This was the first significant environmental ruling from the high court headed by new Chief Justice John Roberts.

Jeremy Emmi, executive director of the Michigan Nature Association said the ruling didn't solve anything and opens the door for hundreds of state cases to determine the law.

"Most people agree wetlands need to be protected," he said. "But this could be the beginning of the end. We can't just keep filling in wetlands because we want to build another strip mall." The court's four most conservative members wanted a more sweeping ruling, clearing the way for development of land unless it was directly connected to waterways.

The court's four most liberal members said that such a ruling would reject three decades of practice by the Army Corps of Engineers and threaten the environment. In the middle was Justice Anthony M. Kennedy who agreed with the overall opinion but not all of Scalia's points.

The Associated Press contributed to this report.