Q151. "Rudy Giuliani seems to be running for President in 2008. But in 2002, Giuliani was given an honorary knighthood by Elizabeth II. I'm wondering if this would place a restriction upon his candidacy?"
A. The relevant part of the Constitution is Article 1, Section 9, Clause 8, which states: "No Person holding any Office ... shall, without the Consent of the Congress, accept of any ... Title, of any kind whatever, from any King, Prince or foreign State." Basically, no one in the government is to take any present, gift, or title from any foreign power.
The first issue is that Giuliani is not a part of the U.S. government — and the Emoluments Clause is pretty clear that it applies to current employees of the government. The Plain Meaning test would probably let Giuliani slide by if he had a title; but a sitting President would be barred from accepting the title.
However, the Emoluments Clause does have a caveat — the acceptance can be authorized by Congress, and Congress has done just that. In 5 USC 7342, Congress authorized the acceptance of "order[s], device[s], ... [or] award[s]" from foreign governments, so long as they are authorized by the employee's department and are of minimal real value. In this code, the President, Vice President, and all members of Congress are considered employees, as are spouses and soldiers.
Generally, titles bestowed upon foreign governments are honorary only, especially within the United States. Many people in government and in private life have been given titles, such as Bill Gates, Ronald Reagan, George H.W. Bush, Norman Schwartzkopf, Wesley Clark, Jerry Lewis, Bob Hope, Collin Powell, Tom Foley, and Charlton Heston.