@Foreign authors?
DavCrav - Since your book is still being written, you don't have to worry about the Google Book Settlement. It only affects books published up till 5 January this year.
Of course, if the publishing industry suffers financial damage owing to, eg, piracy, as a result of Google's scanning books and putting them online, it may affect your chance of finding a publisher.
Whether, if your book is published, Google will scan it without your permission is a question that cannot be answered right now. A lot may depend on whether the Settlement goes through, and in what form.
Even though a book hasn't been published by a US publisher, it is copyright in the US under international law. Under the settlement agreement, everyone who has a US copyright is opted into the settlement, regardless of whether they have been published in the US.
Authors who formally opt out of the Google Book Settlement remain free to sue Google for copyright infringement - but I think the case would be heard in the US and I doubt whether the CPS would get involved. Unfortunately.
As for the WTO's rules on copyright infringement: the short answer is that what's happening is against them, but Google, the Authors Guild and the AAP are trying to get round them using the Settlement.