Whether sanction is applied to "Southern" Sudan?
On April 12, 2011, Office of Foreign Assets Control ("OFAC") in Department of the Treasury announced as a guidance that the sanction to (current) Sudan will continue to be applied, but Southern Sudan will NOT be subject to the sanction. The new state of Southern Sudan will no longer be directly subject to OFAC sanctions.
However, tricky thing is that the guidance indicates that "the sanction will continue to prohibit U.S. persons from dealing in property and interests in property of the Government of Sudan, from performing services that benefit Sudan or the Government of Sudan, from engaging in transactions relating to the petroleum or petrochemical industry in Sudan, and from participating in exports to or imports from the new state that transit through Sudan."
As the map shows, Southern Sudan does not face ocean, surrounded by land boarders, so they have no sea ports for export/import. For international trade with other countries, Southern Sudan may need to rely (current) Sudan in some cases.
Traders should be cautious with this point in interpretation of this OFAC guideline.
(Reference: OFAC guidance http://www.treasury.gov/resource-center/sanctions/Programs/Documents/sudan_secede_guide.pdf )