you cannot legislate technology. Just look at California and their farcial demand for zero emmissions. People won't buy electric cars until they can compete in price and performance.
Remember that 30% of our power comes from renewable sources (wind, hydro, solar), and that is something that is legislated. And that percentage % increases in the near future.
Also, we have legislated the toughest the toughest emissions laws in the country. And all automakers and designing to meet the standards that California has put in place. Why?? Well we have over 30 million people in this state, and California by itsself is the 5th largest economy in the world. It would be unwise to neglect this large portion of the market.
Legislation cannot be written requiring electric cars today because they simply are not feasable. They have poor range. They are very small. And the power grid cannot support 30 million electric cars!
But, if we invest in the devleopment of batteries and solar cells (like I have been advocating in all my posts), then these WILL come down in price, and be very feasible. I believe that California is the place where this will start!