What is Internal Commerce?

Legal Definition
Such as is carried on between individuals within the same state, or between different parts of the same state. Lehigh Val. R. Co., v. Pennsylvania, 145 U. S. 192, 12 Sup. Ct. 806, 36 L. Ed. 672; Steamboat Co., v. Livingston, 3 Cow. (N. Y.) 713. Now more commonly called "intrastate" commerce.
-- Black's Law Dictionary