I came across an interesting article in the March 15, 2008 edition of the Economist related to the Energy Independence and Security Act of 2007 and limitations on US government purchases of crude from oil sands.
It seems the EISA bans federal agencies from buying alternative or synthetic fuels if their production and use result in more greenhouse gases than conventional oil. Processing oil sand crude results in three times the emissions of a barrel of light sweet crude.
Find it a bit surprising that the oil industry lobbyist and the armed forces let that one slip through. I got to believe that this will be overturned in record time or outright ignored.