According to the announcement by Japanese METI on April 8th, Vietnam have limitation of issuance of back-to-back C/O (Country of Origin) in AJCEP, which was implemented in Dec 01, 2008.
Same manner as ordinary C/O, Vietnam's Ministry of Industry and Trade （商工省） have authority to issue AJCEP C/O.
In issuing back-to-back C/O by Vietnam, trader need to understand the commodities must be under control of Vietnam customs. For example, the commodities under bonded area or EPA (Export Processing Zone) are OK to issue back-to-back C/O, but if they are after import customs declaration, Vietnam authority will NOT issue back-to-back C/O, according to the announcement.
This could be operational limitation of making use of back-to-back C/O. For Japan, back-to-back C/O system is first time to handle in AJCEP, the operational guidance or information of back-to-back C/O is not enough so far.
(Source: METI web site http://www.meti.go.jp/policy/trade_policy/090408AJCEPannouncement.pdf - Japanese only)