A federal judge’s ruling last week directing the Obama administration to issue a long-delayed smog standard is reanimating a battle between businesses and environmental groups that has been dormant for three years. The more stringent federal standard for ground-level ozone, commonly known as smog, was delayed by President Barack Obama in 2011. But last Tuesday, a federal court, siding with several environmental and public-health groups, ruled that the Environmental Protection Agency must propose the standard by December and complete it in October 2015. The ozone standard, mandated under the Clean Air Act, isn’t a direct regulation on business. States, however, must comply, which in turn would require businesses and localities that emit smog-forming pollution, including nitrogen oxides and volatile organic compounds, to install new pollution equipment.