This just came to my attention ...
Some of the flame retardants used in making XPS and other products have been banned by Gov Brown (bill AB127) that makes it illegal to sell XPS and many other products in California.
http://forums.jlconline.com/forums/showthread.php?62950-California-to-Ban-Flame-Retardants
http://www.greenbuildingadvisor.com/blogs/dept/green-building-news/california-law-addresses-fire-retardants-homes
http://www.thebuildingcodeforum.com/forum/residential-fire-codes/12807-california-ban-flame-retandants.html
Has anyone in CA noticed the absence of XPS in the stores?