“For the power given to Congress by the Constitution does not extend to the internal regulation of the commerce of a State, (that is to say of the commerce between citizen and citizen,) which remain exclusively with its own legislature; but to its external commerce only, that is to say, its commerce with another State, or with foreign nations, or with the Indian tribes.”Of course, if the Federal Government took this point of view today, it would require wiping out 90% of its economic regulations, not to mention dissolving the Federal Reserve.
"I consider the foundation of the Constitution as laid on this ground: That 'all powers not delegated to the United States, by the Constitution, nor prohibited by it to the States, are reserved to the States or to the people.' To take a single step beyond the boundaries thus specially drawn around the powers of Congress, is to take possession of a boundless field of power, no longer susceptible of any definition."
Note, Jefferson was prompted to state this simply in considering the establishment of a National Bank in 1791. Imagine what he would say today about the encroaching establishment of National Socialism in America*, already half complete.
*Think I'm exaggerating? Read Ed Cline's latest column, on Obama's recent commencement speech at the U of Michigan.