Originally this system was intended to arouse a further intention of emissions reduction promoted by the benefits of trading through the reduction of emissions, but conversely, it is pointed out that the system can lessen essentially needed efforts to reduce the emissions in the following cases: the amount of emissions of the past becomes vested interest or the like depending on a way of assigning the emissions allowances; if the market price of carbon credit becomes lower than the cost of exchange from fossil fuel to renewable energy or of emissions reduction by using energy-saving material.