In the US, State law initiatives have been very effective in reducing greenhouse gas emissions compared to the business-as-usual States. Here is an interactive map showing CO2 emissions per capita in each State and the District of Columbia in 2005. Center for American Progress created it combining the latest available data from the Energy Information Agency with Bureau of Census data.
CO2 emissions for the whole US averaged 20.7 metric tonnes per capita. Nine of the 10 lowest emitting States (includes DC), emitting from 6.77 to 13.36 tonnes per capita, all had in place aggressive state law programs mandating energy efficiency and/or renewable energy mandates, and all have greenhouse gas emission targets. (Idaho didn't but made the clean 10 because of the preponderance of hydroelectric power.) As a consequence, their per-capita emissions are roughly half those of comparable States that do not have such programs.
In all, 36 States had emissions less than 25 tonnes per capita. Eleven higher emitting States ranged from 26.54 to 40.72 tonnes per capita, and then there were four very high emitters, West Virginia (63.3), Alaska (71.8), North Dakota (83.1), and Wyoming (124.21).