I like that. But the form of the policy, whether framed as a fine, tax, or rent, doesn't make much difference. It's like the Henry George proposal that I advocate: some people call it ground-rent while others call it land value tax. You can call it a "rent" or a "tax" but the difference is merely linguistic. But your comment made me realize that something like cap and trade could be seen as logically following from Georgism. I think I'm gonna explore this idea further. Thanks.