Then it follows that there must be US government procurement documents that ban Windows 8 on government computers, as it would be part of the spec. Perhaps someone should tell Reuters, they might have forgot in all the excitement.
That's not how things work. US procurement is not going to leave the OS choice up to a third party so they may require win 7 but there not going to ban win 8. If for no other reason that offline computers are 'secure' enough for testing and the government has a
lot of proprietary apps.
I suspect that whether a given government software spec includes blacklists, whitelists or a combination of both depends largely on who wrote it. Unless someone can show me that exclusive whitelisting is enforced US policy, I would think there will often be documents detailing which versions of software are not to be used on a given contract, as well as which ones are.