If it doesn't stand, it could also set precedent. The fight will probably be closely watched by many riverfront landowners. This issue has been brewing for awhile. Time to make "below the high water mark" the law, with no more "I own to river center" BS.
The chehalis is navigable water. Below the high water is legal and fine to walk. Also the reservations southern border is the river. The whole opposite bank is private/public land.