US Regulatory Activity
In the United States, there have been numerous state and regional agreements made in regards to greenhouse gas emissions. You can find a complete list here (http://www.pewclimate.org/what_s_being_done/targets), but a few notable ones are:
The Regional Greenhouse Gas Initiative (RGGI) is a cooperative effort by 10 Northeast and Mid-Atlantic states to control emissions using a regional cap-and-trade program specifically for power plants.
AB-32, the Global Warming Solutions Act was passed by the California legislature in 2006, and which set up the first enforceable state-wide program in the U.S. to cap all greenhouse gasses.