The Montana Supreme Court says a slough that runs through the Bitterroot Valley property of rock musician Huey Lewis and others is a public waterway and open to recreational use under the state stream access law.

The court overturned a lower court decision that blocked anglers and others from using the Mitchell Slough near Stevensville. The high court’s ruling Monday said the slough is a natural waterway subject to the stream access law.

The law says that even where they flow through private land, Montana rivers and streams are open to all if reached from public property. The waterway between the normal high-water marks belongs to the public.

The 16-mile-long Mitchell Slough splits from the Bitterroot River at Corvallis and rejoins it about 13 miles downstream, near Stevensville. It has been in dispute for years and was the scene in 1990 of the trespassing arrests of two residents who had for years fished in the slough. They were acquitted by a jury.

Lewis and other landowners argued the slough was a private ditch they have transformed over the years and they wanted to keep fishermen away. They said the slough was essentially a canal.

Others, including the Montana Department of Fish, Wildlife and Parks, argued the slough is a channel of the Bitterroot River that, although modified, remains part of the river system. They say it has historically been used for recreation and was first identified as a channel of the river in the 1800s.

A state District Court sided with the landowners in 2006, declaring that the slough was not a “natural” body of water and thus not subject to the stream access law.

A lawyer for FWP argued that, if the lower court decision were to stand, landowners could manipulate waterways, get them declared “not natural”, and declare them private property.

The state Supreme Court said the District Court’s definition of a “natural” waterway was too narrow and that it could easily be applied to bar public access to most of Montana’s rivers and streams.

“The District Court’s dictionary-based definition, which essentially requires a pristine river unaffected by humans in order to be deemed natural, results in an absurdity: For many Montana waters, the (stream access law) would prohibit the very access it was enacted to provide” Justice Jim Rice wrote for the court.

The court’s decision was unanimous, with Helena District Judge Dorothy McCarter sitting in place of Justice W. William Leaphart.