So, it is legal for former owner to retain control over the property of the current owner!? So much for sancrosanctity of private property... Do you know whether anyone tried to test enforcability of those stipulations in court?

Landowners probably do it because they still own some land in the neghborhood and imagine that high rents and businesses that can afford them will keep the value of their reminding plots high. I wonder what empty shop space does for land value...