2 Pet. (27 U.S.) 245 (1829), argued 17 Mar. 1829, decided 20 Mar. 1829 by vote of 6 to 0; Marshall for the Court; Trimble had died. The Willson decision had a double significance: it suggested what has since come to be known as the doctrine of the dormant commerce power; and it was one of several post-1824 cases that constituted Chief Justice John Marshall's retreat from the uncompromising nationalism that characterized the earlier period of his Court.
In Gibbons v. Ogden (1824), Marshall had upheld expansive congressional power under the Commerce Clause and given a broad reading of a federal coastal licensing statute. The Delaware statute challenged in Willson, which permitted a company to erect a dam across a minor navigable stream to drain a swamp, might have been invalidated on the same grounds. Marshall, however, upheld it. He observed in passing that Congress had not enacted any directly pertinent legislation. Hence, Marshall suggested that when Congress chose to allow its commerce power to lie dormant, states could exercise a concurrent power to regulate commerce. This indirectly repudiated an ambiguous hint in Marshall's Gibbons opinion that congressional power over interstate commerce was always exclusive, even when unexercised. The difference in result between the two cases may be explained in several ways. The waterway in Willson was insignificant, the doctrine of state police power was emergent, and the Delaware statute was defensible as a public health measure.
William M. Wiecek