This thread is just filled with uninformed posters. DHS recently asserted that it had the right to require returning citizens to present a passport as proof of citizenship, reversing the previous state of affairs in which the burden of proof -- in the absence of a passport -- was on immigration officials to prove that you were NOT a citizen if you asserted that you were. This assertion may or may not be successfully challenged in court in the near future, but no one, not even the over-reaching morons at DHS have ever tried to claim that they can deny entry to someone presenting a passport. They could assert that it was a forgery, but if they did so and you sued and they were unable to provide credible evidence that your passport was not legitimate, they would be open to all kinds of legal action. If you appear at a US port of entry bearing a legimate passport, there is absolutely nothing legally that can be done to keep you out of the country. Your belief that this can be done arbitrarily and without risk of any consequences to an agent who attempted to do so is completely erroneous.