J. Douglas Gray and Karen Gray owned two lots in Lake Forest. The property was in a historic neighborhood, and the Grays granted a conservation easement to the Lake Forest Open Lands Association. Regarding Lot 2, the conservation easement stated that its purpose was to assure that the property will be retained forever predominantly in its scenic and open-space condition, as lawn and landscaped grounds. The easement prohibited the placement or construction of any buildings whatsoever, or other structures or improvements of any kind on the property. The easement stated that it could only be altered or varied by agreement of both parties or their successors. The easement also stated that it could only be terminated or extinguished, whether in whole or in part, by judicial proceedings in a court of competent jurisdiction. The Grays sold Lots 1 and 2 to John and Liz Draper (defendants). The Drapers decided to install a driveway turnaround on Lot 1 that partially encroached onto Lot 2. The Drapers also decided to change a portion of the landscaping. The Drapers and the Association entered into two amendments of the conservation easement to permit these changes, and the Drapers then installed the driveway turnaround and made the changes. John and Stephanie Bjork and other neighbors (plaintiffs) then sued the Drapers and the Association, alleging that the amendments to the conservation easement were invalid. The trial court determined that the amendments did not materially impair the purposes of the conservation easement and were not otherwise contrary to applicable law or public policy. The plaintiffs appealed.