Comprehensive as the word among is, it may very properly be restricted to that commerce which concerns more states than one. The completely internal commerce of a state, then. may be considered as reserved for the state itself. But, in regulating commerce with foreign nations, the power of Congress does not stop at the jurisdictional lines of the several states. It would be a very useless power if it could not pass those lines. The commerce of the United States with foreign nations is that of the whole United States.
Every district has a right to participate in it.
The deep streams which penetrate our country in every direction pass through the interior of almost every state in the Union, and furnish the means of exercising this right. If Congress has the power to regulate it, that power must be exercised whenever the subject exists. If it exists within the states, if a foreign voyage may commence or terminate at a port within a state, then the power of Congress may be exercised within a state. This principle is, if possible, still more clear, when applied to commerce among the several states. They either join each other, in which case they are separated by a mathematical line, or they are remote from each other, in which case other states lie between them.