 Repeated attempts were made by the Holy Roman Empire, including several efforts over the centuries led by the Emperor himself, to regulate toll collection on the Rhine, but it was not until the establishment of the "Rhine League" of the Emperor, certain nobles, and certain clergy that the control of the "robber barons" over the Rhine was crushed by military force.River tolls on the Rhine, increasingly imposed by states rather than individual lords, remained a sticking point in relations and commerce in the Rhine basin until the establishment of the Central Commission for Navigation on the Rhine in 1815.Michael Heller and Rebecca Eisenberg are academic law professors who believe that biological patents create a "tragedy of the anticommons", "in which people underuse scarce resources because too many owners can block each other."