Castro v. Chicago, Rock Island & Pacific Railroad

“to protect consumers against deceptive designations of the origin of goods and, conversely, to enable producers to differentiate their products from those of others” | a feature of an item may “serve simultaneously as a functional component of a product and a trademark” | the source of the right sued upon, not the ground on which the federal jurisdiction is invoked, determines whether federal or state law applies | ornamental features may fill a consumer need without serving as a trademark even though such features may be nonutilitarian | defendant permitted to manufacture jewelry bearing plaintiffs mark