“Why did you drive so many miles compared to last year? And where did you go and what was the purpose of the trip?” “Can you justify these additional miles which caused you to emit more CO2 than your permit allows?”
I don’t like the idea, but it would be fairer than using the gas tax. I don’t care that the gas tax is not fair, since up until now, you could make choices that might raise or lower the tax you paid. Now they are targeting a subclass of those choices for punishment.
I always object to taxes that are applied unfairly to targeted populations, because the majority loves to tax the minority. Everybody should suffer equally the costs of our government. When the majority can collect the money for government from a minority, they won’t care how much government costs.