In Chapter 10, you’ll see that we recently purchased permits to pollute the air with sulfur dioxide (SO2). We didn’t use the permits: Instead, we threw them out. In other words, we bought permits for the same reason the government buys guns in gun buyback programs—to prevent what we bought from being used. As we discussed in the chapter, gun buyback programs have failed. So why is our plan to buy permits more likely to get SO2 out of the air than the government’s plan to get guns off the street?