Page:Joseph Story, Commentaries on the Constitution of the United States (1st ed, 1833, vol I).djvu/462

 422 the tenth section of the same article declares, that &apos;no state shall, without the consent of congress, lay any imposts or duties on imports or exports, except for the purpose of executing its inspection laws.' Hence would result an exclusive power in the Union to lay duties on imports and exports, with the particular exception mentioned. But this power is abridged by another clause, which declares, that no tax or duty shall be laid on articles exported from any state; in consequence of which qualification, it now only extends to the duties on imports. This answers to the second case. The third will be found in that clause, which declares, that congress shall have power 'to establish an uniform rule of naturalization throughout the United States.' This must necessarily be exclusive; because, if each state had power to prescribe a distinct rule, there could be no uniform rule." The correctness of these rules of interpretation has never been controverted; and they have been often recognised by the Supreme Court.

§ 437. The two first rules are so completely self-evident, that every attempt to illustrate them would be vain, if it had not a tendency to perplex and confuse. The last rule, viz. that which declares, that the power is exclusive in the national government, where an authority is granted to the Union, to which a similar authority in the states would be absolutely and totally contradictory and repugnant, is that alone, which may be thought to require comment. This rule seems, in its own nature, as little susceptible of doubt, as the others in reference to the constitution. For, since the constitution has declared, that the constitution and laws, and treaties in