I appreciate the homework you have done talking to those who say "it can't happen because it hasn't happened and there are laws against it happening.' Now a little research about where it has happened might make a great addendum. For example the city of Pittsburgh has passed such an initiative. See CELDF.org for the fascinating creative legal thinking behind i 103 and the many other similar laws and initiatives across the country.

As for the to you ludicrous idea of protecting our natural environment through creative legislation google Ecuador constitution. Why not start change at the local level by creating fault lines and contradictions? What do you think we should be doing instead?