In 1868 it was affirmed, in an Act passed by the Congress of the United States, that ``the right of expatriation is a natural and inherent right of all people''. I do not know how far this would be taken to imply that a man has a moral right to leave his country whenever he finds it convenient---provided no claims except those of Patriotism retain him there. But if it was intended to imply this, I think the statement would not be accepted in Europe without important limitations: though I cannot state any generally accepted principle from which such limitations could be clearly deduced.

ME Book 3 Chapter 4 Section 5