The market mechanism for de facto regulation of pollution etc - selling the privilege for money - only works if the price is at least approximately the cost of the behavior. It's a way of removing the temptation of externalizing one's costs. But it will only work for some pollutants - one must be able to monitor and source the pollutant, apprehend the perp and enforce the fines, arrive at legally defensible but still realistic estimates of the costs, etc. As we saw with BP in the Gulf, those are hard things to do. Ban and coercive regulation are much cheaper and easier. And I will bet th Germans know that - and that there are some pollutants no one is allowed to dump in the Rhine for any price.