[mywittyname]

> Is freedom of movement within the United States explicitly part of the Constitution?

Interesting question. Not explicitly, but the Federal Government reserves the right to regulate "interstate commerce," which is a power granted specifically to prevent hard state borders, among other things.

States/municipalities do have mechanisms to screw with people from other states via tax and transportation manipulation. But, for the most part, I've never heard of any animosity towards local residents from other states, and I live and work in a city whose metro-area spans three states. Immigrants from other regions are different beast though.