On the imposition of uniform duties of customs, trade, commerce, and intercourse among the States, whether by means of internal carriage or ocean navigation, shall be absolutely free.
But notwithstanding anything in this Constitution, goods
imported before the imposition of uniform duties of customs into any State, or
into any Colony which, whilst the goods remain therein, becomes a State,
shall, on thence passing into another State within two years after the
imposition of such duties, be liable to any duty chargeable on the importation
of such goods into the Commonwealth, less any duty paid in respect of the
goods on their importation.