The International Energy Conservation Code (IECC) energy standard specifies the minimum energy-related requirements for a building or major renovation in a jurisdiction that has adopted this standard. The standard in its entirety can be obtained at the ICC.
The latest version of the IECC is 2012 but any one jurisdiction may instead adopt:
an older version of the IECC,
any published version of ASHRAE 90.1
or nothing at all in home rule states.
Yes, the DOE has ruled that all states must have an energy code at least as stringent as 90.1-2010 but, so far, has not shown an inclination/ability to enforce that.
And anytime a jurisdiction adopts a standard as their energy code, they frequently make modifications to that standard. This site does NOT cover any such modifications.
Certification statements by the States must be provided by May 17, 2014 including showing that they have an residential energy code as least as stringent as IECC-2012. See the Federal Register announcement for details.