-Constitution of the United States of America Article I sec 9
The award of the peace prize to a sitting President is not unprecedented. But Theodore Roosevelt and Woodrow Wilson received the honor for their past actions: Roosevelt's efforts to end the Russo-Japanese War and Wilson's work in establishing establish the League of Nations. Obama's award is different. It is intended to affect future action. As a member of the Nobel Committee explained, the Prize should encourage Obama to meet his goal of nuclear disarmament. It raises important legal questions for the second time in less than 10 months -- questions not discussed, much less adequately addressed anywhere else.Source
The five-member Nobel commission is elected by the Storting, the Parliament of Norway. Thus the award of the peace prize is made by a body representing the legislature of a sovereign foreign state. There is no doubt that the Nobel Peace Prize is an "emolument" ("gain from employment or position," according to Webster).
An opinion of the U.S. Attorney General advised, in 1902 that "a simple remembrance," even "if merely a photograph, falls under the inclusion of 'any present of any kind whatever.' " President Clinton's Office of Legal Counsel, in 1993, reaffirmed the 1902 opinion, and explained that the text of the clause does not limit "its application solely to foreign governments acting as sovereigns." This opinion went on to say that the Emolument Clause applies even when the foreign government acts through instrumentalities. Thus the Nobel Prize is an emolument, and a foreign one to boot.