The Tokyo Metropolitan Government will implement a system requiring new buildings to install solar panels, insulation, and energy conservation starting in April 2025. This is a policy aimed at achieving a “carbon half” 50% reduction in greenhouse gas emissions in Tokyo by 2030. It is projected that 70% of residential buildings and 50% of all buildings in Tokyo will be replaced by new construction by 2050. Some have opposed the mandate on the grounds that it would lead to involvement in genocide, such as forced labor in the Xinjiang Uygur Autonomous Region, where many solar panels are manufactured, an increased economic burden, and concerns about solar power generation. Under the system, major builders supplying more than 20,000 m2 of total floor space in Tokyo would be obligated to install solar power generation equipment in newly constructed buildings. Another system is the Tokyo Metropolitan Government’s ordinance on rooftop greening, the “Nature Conservation Ordinance (Ordinance on the Protection and Restoration of Nature in Tokyo). Greening is mandatory for new construction and expansion of buildings on sites of a certain size. Tokyo’s CO2 emissions in Tokyo are thought to be 70% of the energy consumption of buildings in the business and residential sectors combined, and the calculation is to achieve “carbon half” by maximizing the use of the roofs of new buildings.