You state that "if you drive a car you are literally contributing to global warming" which implies the policy statement "if it is illegal to drive a car, contribution to global warming decreases" and use this to imply it's not a rational argument to make it illegal to drive cars.

To your great surprise, I will now state that it is actually already illegal to drive cars, and it actually does have the exact effect that you say is not a rational conclusion:

http://www.dmv.org/articles/what-to-do-if-your-car-fails-an-...

Today, today, it is literally illegal to drive a car....which doesn't meet EPA standards! As a direct effect, people do not buy and drive cars which fail emissions standards.

So, yes, the exact policy suggestion that you don't go quite as far as to argue for actually is being enforced and actually demonstrably has the exact effect that you (only imply) doesn't happen.

Since you don't even imply any policy conclusions for the other two points I can't address them, I have no idea why you would mention them.

(If the government made it illegal to collect or pay taxes, obviously its tax base would evaporate overnight, this goes without saying, nobody would illegally pay money to the government out of civic duty despite its now being illegal to do so.)

Buying elephant tusks promotes the killing of elephants, regardless of where they came from because the demand you created supports a price in favor of bad actors as well.