If you look on the instructions of the W7 it clearly states an "apostille" is needed if you do not have your documents notarized at a US embassy. This is only necessary if the spouse lives outside the US.
http://www.irs.gov/pub/irs-pdf/fw7.pdfYou can submit copies of original documents if you do any of the
following.
c Have the copies certified by the issuing agency or official
custodian of the original record.
c Have the copies notarized by a U.S. notary public legally
authorized within his or her local jurisdiction to certify that the
document is a true copy of the original. To do this, the notary must
see the valid, unaltered original document and verify that the copy
conforms to the original. U.S. notaries public are available at U.S.
embassies and certain consulates worldwide.
c Have the copies notarized by a foreign notary. However, foreign
notaries are only acceptable as outlined by the Hague Convention.
The Hague Convention provides for the simplified certification of
public (including notarized) documents to be used in countries that
have joined the Convention. A certification will be issued in the form
of an "apostille," which will be attached to the copy of the
document.
Note. The apostille must stay attached to the copy of the document
when it is sent to the IRS.