From the 2011 National Geographic Photo Contest Rules:
Contest is open only to individuals who have reached the age of majority in their jurisdiction of residence at the time of entry and who do NOT reside in Arizona, Cuba, Iran, New Jersey, North Korea, the Province of Quebec, Sudan, Syria or Vermont.Well, there is an explanation of this amazing list of excluded places. Here and here. And a totally incomprehensible item here.
But could the list have been arranged differently? A good question, that...
Hat tip: T.G.-V.