Article 6, Clause 2
Alexander Hamilton, Federalist, no. 33, 207--82 Jan. 1788
But it is said, that the laws of the Union are to be the supreme law of the land. But what inference can be drawn from this or what would they amount to, if they were not to be supreme? It is evident they would amount to nothing. A LAW by the very meaning of the term includes supremacy. It is a rule which those to whom it is prescribed are bound to observe. This results from every political association. If individuals enter into a state of society the laws of that society must be the supreme regulator of their conduct. If a number of political societies enter into a larger political society, the laws which the latter may enact, pursuant to the powers entrusted to it by its constitution, must necessarily be supreme over those societies, and the individuals of whom they are composed. It would otherwise be a mere treaty, dependent on the good faith of the parties, and not a government; which is only another word for POLITICAL POWER AND SUPREMACY. But it will not follow from this doctrine that acts of the larger society which are not pursuant to its constitutional powers but which are invasions of the residuary authorities of the smaller societies will become the supreme law of the land. These will be merely acts of usurpation and will deserve to be treated as such. Hence we perceive that the clause which declares the supremacy of the laws of the Union, like the one we have just before considered, only declares a truth, which flows immediately and necessarily from the institution of a Foederal Government. It will not, I presume, have escaped observation that it expressly confines this supremacy to laws made pursuant to the Constitution; which I mention merely as an instance of caution in the Convention; since that limitation would have been to be understood though it had not been expressed.
Though a law therefore for laying a tax for the use of the United States would be supreme in its nature, and could not legally be opposed or controuled; yet a law for abrogating or preventing the collection of a tax laid by the authority of a State (unless upon imports and exports) would not be the supreme law of the land, but an usurpation of power not granted by the constitution. As far as an improper accumulation of taxes on the same object might tend to render the collection difficult or precarious, this would be a mutual inconvenience not arising from a superiority or defect of power on either side, but from an injudicious exercise of power by one or the other, in a manner equally disadvantageous to both. It is to be hoped and presumed however that mutual interest would dictate a concert in this respect which would avoid any material inconvenience. The inference from the whole is--that the individual States would, under the proposed constitution, retain an independent and uncontroulable authority to raise revenue to any extent of which they may stand in need by every kind of taxation except duties on imports and exports. It will be shewn in the next paper that this CONCURRENT JURISDICTION in the article of taxation was the only admissible substitute for an intire subordination, in respect to this branch of power, of the State authority to that of the Union.