I don't buy this, and I'm very much against the principle of having laws that don't specify how to achieve things. The result has been that for several decades

I don't buy this, and I'm very much against the principle of having laws that don't specify how to achieve things. The result has been that for several decades manufacturers have been meeting emissions targets by plain manipulation, whether it's dieselgate or it's creating ECU maps tailored for the test driving cycle. We have achieved only emissions reductions on paper, when we could have been mandating PHEVs and actually solving problems. If you look back at when California was actually able to do something about their smog problem, it was through mandating specific technologies - first it was positive crankcase ventilation, then catalytic converters.