If your target is absolutely zero emissions, you also have to ban volcanos, limestone erosion, permafrost melting, cows, humans, and really all animal life on earth. There are plenty of natural processes that result in CO2 being released into the air, not least of which is breathing.

Grandparent post has a "perfect is the enemy of the good" fallacy. Banning all emissions is simply not possible. That doesn't mean that efforts to limit emissions aren't worthwhile. And that's what cap & trade programs do; the government sets a cap on carbon emissions based on the best available science for what the planet can tolerate before we get unacceptable levels of warming, and then companies can trade carbon credits amongst themselves to allocate who reduces their emissions and who pays other people to reduce their emissions.