52. No evil contributed more to the feebleness of the old Confederation than its inability to regulate commerce. The mischief being great, the grant of power to correct the mischief was correspondingly great. This grant of power to regulate commerce comprehends “all foreign commerce and all commerce among the States.” As inefficiency was the evil, the grant of power was to secure efficiency. In construing this grant—the commerce clause of the Constitution—the large and single purpose is so to construe as not to impair its efficiency and thus defeat the object of the grant.[133]
The commerce clause has become the authority for exercising the enormous powers of the national government as is illustrated, possibly, by the exercise of power under no other clause. This means that the United States in exercising this delegated power exercises so vast a power that it seems to be sovereignty itself. Vast as this power is—and practically it is incommensurable—it is a delegated, not an original power of the national government. The scope, purpose, and nature of this national power to regulate commerce are indicated by the Supreme Court in its construction of the commerce clause. Here as in the exercise of the taxing power the test is jurisdiction. The essential question is, What is the jurisdiction of the United States, what that of the respective States over commerce?
53. Commerce is intercourse,[134] and comprehends traffic, navigation, telegraphic intercommunication, and consequently, communication by telephone, wireless, or signals.[135]
The Constitution empowers Congress to regulate commerce “among the several States,” an expression which excludes “the completely interior traffic of a State.” This completely internal commerce is reserved for the State itself. To whatsoever extent the foreign or interstate commerce of the United States penetrates a State, it is subject to regulation by the United States; it is carried on within national jurisdiction. The power of Congress to regulate commerce within this jurisdiction is complete in itself and knows no limitations other than these prescribed in the Constitution. Thus this power to regulate commerce, though limited to commerce with foreign nations and among the States, and with the Indian tribes, is plenary as to these objects, and Congress in exercising this power is commonly spoken of as “sovereign.”[136] It follows, that as the Constitution is the supreme law of the land, and the Supreme Court has power to say what the law is—State laws to regulate commerce, in conflict with national laws, are unconstitutional. The essential issue, in such conflict, is one of jurisdiction. And here, the real question is whether the regulation of commerce by a State is essential to its existence as a State, or regulation by the United States is essential to its existence as the United States. Such regulation by a State is known as the exercise of the police power.[137]
But the United States also possesses police power. The line of demarcation between the State and the national police power follows closely, if not precisely, the line of demarcation between State power and national power to regulate commerce.[138] The State has power to protect itself,—that is, to guard its people against contagious or infectious diseases, as is exemplified in laws for the inspection of foods, for forbidding the pollution of streams, for securing the accuracy of weights and measures, the peace and good order of communities, the comfort of the inhabitants,—and, in a word,—to exercise such authority as, were no such authority exercised, the State would cease being the State.
54. The power granted to Congress to regulate commerce is not a power granted to the States; it pertains to the United States only. Therefore Congress has no power to regulate commerce that is not “with foreign nations, and among the several States, and with the Indian tribes.” Practically this deprives the State of police power over foreign and interstate commerce, and deprives the United States of police power over commerce that is, as to the State, completely internal. To what extent a State can protect itself from the entrance of paupers, insane or diseased persons, is a question for determination by the Courts. If such persons are “commerce” their entrance is a matter within the jurisdiction of Congress. But the welfare of the people of the United States is essentially the welfare of the people of the States, and Congress, in considering that welfare, avoids possible conflict with State legislation. Thus the immigration laws—all of which are national—include, or seek to include, these provisions for inspection which a State would prescribe, in the exercise of its police power for the health, safety, and general welfare of its own citizens. But here, too, a dominant principle prevails;
The government of the United States, within the scope of its powers, operates upon every foot of territory under its jurisdiction. It legislates for the whole nation, and is not embarrassed by State lines. Its peculiar duty is to protect one part of the country from encroachments by another upon the national rights which belong to all.[139]
Tested by this principle, any State laws conflicting with national immigration laws are unconstitutional.
55. The power to regulate commerce among the several States extends to commercial highways and to agencies employed in such commerce. Thus waterways capable of navigation and the free and unobstructed use of them are subjects of congressional legislation under the commerce clause. From this it follows that Congress legislates concerning these waterways, their protection, their dredging, the bridges that cross them, the boats that navigate them, the form, size, construction, command, and equipment of these boats, the inspection of boilers, the licensing of officers,—indeed, concerning navigation in its broadest application under the commerce clause. Vessels engaged in such commerce are described as “the public property of the nation, and subject to all the requisite legislation of Congress.”[140]
56. In like manner, the national power to regulate commerce extends over interstate commerce when carried on by land transportation. Thus cars on railroads used in interstate commerce must be equipped with automatic couplers and continuous brakes, and locomotives with driving-wheel brakes.[141]