Many countries have value-added taxes that are paid by producers but are intended to fall on consumers. (They're basically just an indirect way of imposing sales taxes.) Such value-added taxes are always accompanied by an equal tax on imports; such import taxes are considered legal because, like the value-added tax, they're really an indirect way of taxing all consumer purchases at the same rate. Compare this situation to the argument over carbon tariffs. Why might defenders argue that such tariffs are legal? What objections can you think of?