Article I, Section 8, Clause 3:
[The Congress shall have Power . . .] To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes; . . .
We are now arrived at the inquiry – what is this power? continued the Chief Justice.
It is the power to regulate; that is, to prescribe the rule by which commerce is to be governed. This power, like all others vested in congress, is complete in itself, may be exercised to its utmost extent, and acknowledges no limitations, other than are prescribed in the constitution . . . If, as has always been understood, the sovereignty of congress, though limited to specified objects, is plenary as to those objects, the power over commerce with foreign nations, and among the several states, is vested in Congress as absolutely as it would be in a single government, having in its constitution the same restrictions on the exercise of the power as are found in the constitution of the United States. 1
Of course, the power to regulate commerce is the power to prescribe conditions and rules for the carrying-on of commercial transactions, the keeping-free of channels of commerce, the regulating of prices and terms of sale. Even if the clause granted only this power, the scope would be wide, but it extends to include many more purposes than these.
Congress can certainly regulate interstate commerce to the extent of forbidding and punishing the use of such commerce as an agency to promote immorality, dishonesty, or the spread of any evil or harm to the people of other states from the state of origin. In doing this, it is merely exercising the police power, for the benefit of the public, within the field of interstate commerce. 2 Thus, in upholding a federal statute prohibiting the shipment in interstate commerce of goods made with child labor, not because the goods were intrinsically harmful but in order to extirpate child labor, the Court said:
It is no objection to the assertion of the power to regulate commerce that its exercise is attended by the same incidents which attend the exercise of the police power of the states. 3
The power has been exercised to enforce majority conceptions of morality, 4 to ban racial discrimination in public accommodations, 5 and to protect the public against evils both natural and contrived by people. 6 The power to regulate interstate commerce is, therefore, rightly regarded as the most potent grant of authority in section 8.