The constitutionality of a protective tariff, that is, a system of customs duties levied on foreign imports so arranged as to furnish incidental protection to home industries, though questioned in earlier years, has now passed beyond the range of controversy. Such laws being on their face revenue measures, may not be questioned because their effect, and indeed the intent of the legislature, is primarily to supply protection rather than revenue. The doctrine of the court in McCray v. United States49 is conclusive as to this. But even if this were not so, a tariff avowedly levied primarily and solely for protection is constitutionally justified under the grant of authority to Congress " to regulate commerce with foreign nations." 50