If you are paying for the energy, you should be able to use it. The logical next step to limiting sale of devices that use too much energy is to start punishing individuals for using too much energy. After all I can buy three energy efficient video cards and Crossfire them, using more power than a single energy efficient GPU, so better just limit the amount of energy per person in a household and impose harsh penalties on households that violate this cap. This is the same problem I see with 16oz limit on soda drinks in NY. People who want to drink more soda will buy several sodas. People who want more performance from their PC will buy more devices when possible if government limitations make a single device inadequate to meet their needs.
If you impose a limit on a single factor, say energy consumption per unit or calories per drink, people will buy more GPU's or more sodas. You need to convince people that using less energy (or getting less empty calories) is in their best interest if you truly want to enact change. You'll never convince everyone, but just look at the amount of people who are recycling voluntarily today compared to 10 years ago. We didn't have to arrest anyone for generating too much trash either.
Ultimately, I just don't think an "Iron Fist" approach to energy conservation such as this will have any meaningful effect, and will clearly limit the personal freedom of individuals who are graphics enthusiasts, so as an advocate of personal freedom I am against this type of thing, and I think many others would agree.