Melville Fuller

“ The power vested in congress to regulate commerce among the several states is the power to prescribe the rule by which that commerce is to be governed; and, as that commerce is national in its character, and must be governed by a uniform system, so long as congress does not pass any law to regulate it, or allowing the states to do so, it thereby indicates its will that such commerce shall be free and untrammeled. ”

“ In whatever language such legislation may be framed, its purpose must be determined by its natural and reasonable effect; and the presumption that it was enacted in good faith cannot control the determination of the question whether it is or is not repugnant to the constitution of the United States. ”

“ The natural and reasonable effect of this statute is to prevent the sale of oleomargarine because it looks like butter. How this resemblance, although it might possibly mislead a purchaser, renders it any the less an article of commerce, it is difficult to see.
I deny that a state may exclude from commerce legitimate subjects of commercial dealings because of the possibility that their appearance may deceive purchasers in regard to their qualities. ”