You never see it posted. There is certainly permission now, and it's in the wake of a class action lawsuit.
I should indicate that the networks didn't volunteer this up. They did everything they could for a great many years to hold off any surcharging, but it is allowed in a lot of other jurisdictions, and not unlike most of those other jurisdictions, retailers tend not to surcharge. They do that because ultimately they're concerned that they will see a loss of business. If it were commonplace, perhaps more would do so, but nobody wants essentially to commit seppuku by being the first to surcharge. Therefore, in essence, it's a right without much of a remedy.