Washington State has adopted the 2006 International Building Code (including the IFC), with state-specific changes.

Basically, a company called the International Code Council puts together model codes, which states can adopt and apply their own changes to. The state-specific changes are generally available on their websites (http://www.sbcc.wa.gov/sbccindx.html for WA), but the base code itself--and the code books with the state modifications inserted-- are not publically available except in libraries, because the ICC makes their money by selling copies of their code (which is copyrighted).