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; . . .
All grants of power to Congress in § 8, as elsewhere, must be read in conjunction with the Necessary and Proper Clause, § 8, cl. 18, which authorizes Congress
[t]o make all Laws which shall be necessary and proper for carrying into Execution the foregoing powers. Chief Justice Marshall alluded to the power thus enhanced by this clause when he said that the regulatory power did not extend
to those internal concerns [of a state] . . . with which it is not necessary to interfere, for the purpose of executing some of the general powers of the government. 1 There are numerous cases permitting Congress to reach
purely intrastate activities on the theory, combined with the previously mentioned emphasis on the cumulative effect of minor transactions, that it is necessary to regulate them in order that the regulation of interstate activities might be fully effectuated. 2 In other cases, the clause may not have been directly cited, but the dictates of Chief Justice Marshall have been used to justify more expansive applications of the commerce power. 3