On the other hand, in Kelly _v._ Washington,[848] decided in 1937, the Court sustained the State in applying to motor-driven tugs operating in navigable waters of the United States legislation which provided for the inspection and regulation of every vessel operated by machinery if the same was not subject to inspection under the laws of the United States. It was conceded that there was "elaborate" federal legislation in the field, but it was asserted that the Washington statute filled a gap. "The principle is thoroughly established," said Chief Justice Hughes for the Court, "that the exercise by the State of its police power, which would be valid if not superseded by federal action, is superseded only where the repugnance or conflict is so 'direct and positive' that the two acts cannot 'be reconciled or consistently stand together.'"[849] And in Bob-Lo Excursion Co. _v._ Michigan,[850] the Court, elbowing aside a decision of many years standing,[851] ruled that the commerce clause does not preclude a State, in the absence of federal statute or treaty, from forbidding racial discrimination by one carrying passengers by vessel to and from a port in the United States to an island situated in Canadian territory.
The holding in Willson _v._ Blackbird Creek Marsh Co.[852] has been invoked by the Court many times in support of State legislation permitting the construction across navigable streams of dams, booms, and other shore protections,[853] as well as in support of State legislation authorizing the erection of bridges and the operation of ferries across such streams.[854] Bridges, it is true, may obstruct some commerce, but they may more than compensate for this by aiding other commerce.[855] In Justice Field's words in Huse _v._ Glover,[856] it should not be forgotten that: "the State is interested in the domestic as well as in the interstate and foreign commerce conducted on the Illinois River, and to increase its facilities, and thus augment its growth, it has full power. It is only when, in the judgment of Congress, its action is deemed to encroach upon the navigation of the river as a means of interstate and foreign Commerce, that that body may interfere and control or supersede it. * * * How the highways of a State, whether on land or by water, shall be best improved for the public good is a matter for State determination, subject always to the right of Congress to interpose in the cases mentioned."[857] The same principle applies to the construction of piers and wharves in a navigable stream,[858] as well as to harbor improvements by a State for the aid and protection of navigation;[859] and reasonable tolls may be charged for the use of such aids, and reasonable regulations laid down governing their employment.[860]