We will just import more from other nations or states and prices may go up slightly.  Oil is a global commodity and we must think globally about it.  Oil can easily go to the California refineries from Venezuela, Mexico, Canada, Wyoming, Montana, North and South Dakota.  California probably uses all of its oil production but I don't know.  Heck, it might even be economically worth it to build a refinery or two in Oregon.  Shutting Alaska oil down could very well set-off an economic boom in Oregon.