A tiny plot of shore land on the federally protected St. Croix River has become a significant legal battleground over private property rights.

Attorneys for the children of William and Margaret Murr filed an opening brief Monday in their appeal to the U.S. Supreme Court contending that St. Croix County wrongly blocked them from selling a vacant waterfront parcel. The Murr family said they wanted to sell the 1.25-acre lot to finance improvements to their three-bedroom family cabin, built on an adjoining lot south of Hudson, Wis., soon after the parents bought the property in 1960.

St. Croix County said that regulations governing the St. Croix prohibited such land use, but Monday’s filing alleged the county’s denial of the sale violated the Fifth Amendment because it amounts to a “taking” of private property for public use without just compensation.

“This is a desirable neighborhood with many high-value newer homes and waterfront parcels that are especially valuable and highly desired by purchasers,” attorney John M. Groen of the Pacific Legal Foundation wrote in Monday’s brief.

The foundation, a national property rights watchdog organization that believes in “a balanced approach to environmental regulations in courts nationwide,” said the Murr case potentially could resolve a major and recurrent issue in property rights law. The “precedent-setting” case will decide whether government can view two contiguous parcels of land as a “parcel as a whole” and thereby deny the property owner “just compensation” for taking away use of one of those parcels, the foundation said.

To the opposing side, the Murr case challenges well-known regulations that protect the beauty and water quality of the Lower St. Croix River, which Congress added to the National Wild and Scenic Rivers program in 1972.

The intent of those regulations is to minimize overcrowding and pollution along the river from overdevelopment, said attorney Remzy Bitar, who will represent St. Croix County’s argument in the Supreme Court. The legal battle ensued 10 years ago when the county denied the Murrs’ variance requests, Bitar said.

“I think the record shows they’re familiar with not just the beauty of the riverway but they were aware of these regulations for a long time and value them as much as any other citizen,” he said.

‘Family legacy’

In 1960, the Murrs bought a lot on the St. Croix River under the business name William Murr Plumbing Inc., where they soon built their 950-square-foot cabin in Troy, a rural town of about 4,300 residents. “And so began a family legacy of enjoying many summers and weekends at the lake,” Monday’s brief said, referring to the wide portion of the St. Croix River known as Lake St. Croix.

In 1963, “recognizing the long-term potential of the area,” the Murrs bought a second parcel next to their cabin. The Murrs planned to develop the second parcel or sell to a third party when the “investment ripened,” the brief said.

In 1994, the parents transferred ownership of the cabin parcel to their six children as a gift. A year later, the parents transferred the second parcel to their children. Four of the children — Joseph, Michael and Donna Murr, and Peggy Heaver — now own both parcels, Monday’s brief said.

In 2004, the children decided to make improvements to the cabin, including elevating it to diminish flood threats. They intended to sell the vacant parcel to finance the work. However, county planning officials told them that because they owned both parcels, they couldn’t sell the vacant one without selling the other. Zoning regulations adopted in 1975 would treat both parcels as one, the brief said.

The Murrs were “flabbergasted,” initiating a series of court actions that led to the nation’s highest court, scheduled to hear oral arguments in October.

“The investment parcel is legally distinct, purchased by their parents at a different time, and was taxed as a distinct parcel,” said Harold Johnson, a Pacific Legal Foundation spokesman.

But attorneys for St. Croix County “have a very different view of the facts,” Bitar said, and regulations governing land along the St. Croix are unique to a federally protected river.

“If the parcels were sitting in an agricultural district a mile or two off the riverway, circumstances of this case may vary greatly,” he said.

Bitar said St. Croix County will file its response to the Murr brief in June.