The USDA website has moved or removed many of the relevant documents, and I'm far to lazy to track them down... You will find them still reference in Google and on many other sites with quotes, but the USDA site itself has many 404 page not found errors...
Here is one though, from a FOIA request, scroll down to their reply on the page 5...
http://www.aphis.usda.gov/foia/foia...provided in request 11-089/11-089 Records.pdf
"the agency has no authority to regulate products created by mutagenesis techniques"
Thus we apply legal logic, if the USDA has no authority to regulate mutanenic products then they can not regulate their exclusion in organics...
This write up has a lot of reference links, scroll to about page 25, but again many links are not dead, even those on the USDA site... But, it eludes to multiple letters like the above where the USDA has stated they have no authority to regulate mutant crops...
http://animalscience.ucdavis.edu/an...ntations/2013/TrransgenicAnimalConference.pdf
Also as a simple verifiable proof, go back to my previous post in regards to the Rio Red (Rio Star) Grapefruit (Google it's history) it is in fact a product of radiation exposure and mutation, yet it's readily sold as organic as long as it was grown by organic standards... Just wait until this fall, you can find them labeled as 'certified organic' all over the place, even at Whole Foods, LOL...
Feel free to Google these terms as a starting point on further research...
Mutation Breeding
Mutagenesis
Cell Fusion
Or Google the phrase I quoted above for further reading, include the quotes in the search "no authority to regulate products created by mutagenesis"
Wow yeah, thanks for looking all that up! I am entirely too lazy...lol
Reminds me of the magic of Colchicine... All natural from my autumn crocus, magic polyploidy mutations for getting female seed... That's why I changed my major to agronomy lol... No, "Dolly" clones and eating corn with BT toxins meant to blow up bugs from the inside just weren't my cup of tea

The good old misleading, vague statements... "No authority"... Ugh that's so frustrating on all fronts!