WASHINGTON The Supreme Court this week admonished the Environmental Protection Agency for overreaching in regulating greenhouse gases. The Clean Air Act covers polluters that emit 250 tons per year (or in some cases, 100 tons). This standard makes no sense if applied to greenhouse gases. Thousands of establishments from elementary schools to grocery stores would be, absurdly, covered. So the EPA arbitrarily chose 100,000 tons as the carbon dioxide threshold.