What are the USDA's regulations regarding the import of Mangosteens
from various countries (i.e. what countries of origin would
mangosteens be allowed into the US from)?  Are there special steps or
treatments required before the fruit would be allowed into the US?  If
so, what are they?  Specific to import from Thailand, is there any
sort of treatment that if used, would permit the fruit into the US? 
Also I have heard that the USDA has a new treatment in the works and
they plan to allow mangosteens from Thailand into the US sometime next
year, if they have been treated in this manner.  Can someone confirm
that this is correct and tell me what the new treatment method is? 
Please provide me with the source for your information.  Thanks!

I did not find sufficient data to answer your question.  Helpful
information may be that mangosteens are often clumped with mangos and
guavas in the statistics.  Here is the list of documents relating to
fruit inspection:
AGRICULTURAL MARKETING SERVICE1 (Standards, Inspections, Marketing
Practices) DEPARTMENT OF AGRICULTURE
PART 51--FRESH FRUITS, VEGETABLES AND OTHER PRODUCTS (INSPECTION,
CERTIFICATION, AND STANDARDS)

http://www.access.gpo.gov/nara/cfr/waisidx_02/7cfr51_02.html

The main government agency involved with inspection is the US Dept of
Agriculture, Animal and Plant Health Inspection Service.  Their web
site:

http://www.aphis.usda.gov/index.shtml

In case a researcher cannot answer this for you, perhaps a freight
forwarder acquainted with the current procedures and regulations may
be able to advise you.

historybuff

Unfortunatly, I've learned the hard way that the regulations for
mangosteens are not the same as for mangos or guavas.  I have also
looked at the site you posted and have been unable to come up with the
information I was looking for.  In addition, I have been in contact
with a freight fowarder (whom I had hired to clear a shipment of
mangosteens from Thailand - which it turned out, had to be
incinerated) and he has been unable to help me.

It sounds as if we've both exhaused the online resources.  My best
suggestion is to go back to the documents relating to the last
shipment and incineration and look for the reason given for denial of
entry.  I would guess there is some sort of code listed that indicates
exactly what regulation prevented the import. Tracking it that way may
lead you to someone in the Dept of Ag who can give you a copy of the
specific regulations.

The reason give for the denial of entry was "Restricted" and the
package was marked hold/destroy.  The customs broker/freight fowarder
whom I hired said that they found pests on the fruit that would
devastate the US agricultural industry if they entered the
environment.  He also told me that in the past he has been permitted
to treat agrigultural products while in holding and then clear them,
but when an item is restricted, it means no entry, no way, no how.  I
have been unable to find a domestic grower of the fruit, yet I have
(on rare occasions) seen mangosteens at the fruit market in New York's
Chinatown.  Therefore, I am trying to find out where they are imported
from and if they were treated, what method was used.  The reason I am
interested in Thailand specifically is because I am working with an
exporter there (who sent me the first shipment) which was denied
entry, and he has heard that the USDA will allow mangosteens from
Thailand next year and he has asked me to confirm this.

I did quite a bit of additional searching but found nothing
specifically marking mangosteens as restricted.  The problem could be
the nature of the pest they found rather than the specific fruit.

I have had the same results - unable to find anything that even
remotely designates mangosteens as restricted.  However, when I
attempted to order mangosteens from a fruit company in Australia, they
said that US protocols would not allow them to ship to me.  Also, I
have been told the following by another google researcher:  "According
to this web page, they're (mangosteens) hard to find in the U.S.
because there is a prohibition on their import from Asia. I guess
that's what the Australian firm was talking about. It does say that
mangosteens may be imported from the Carribean, but it doesn't offer
specifics. http://www.mangosteens.com/faq.htm"  I have just e-mailed
the Chief of the Fresh Products Branch of the USDA and am awaiting a
response.  My fingers are crossed.