Until Congress shall otherwise provide all laws now imposing taxes in the said West Indian Islands, including the customs laws and regulations, shall, insofar as compatible with the changed sovereignty and not otherwise herein provided, continue in force and effect, except that articles the growth, product, or manufacture of the United States shall be admitted there free of duty: Provided, That upon exportation of sugar to any foreign country, or the shipment thereof to the United States or any of its possessions, there shall be levied, collected, and paid thereon an export duty of $6 per ton of two thousand pounds, irrespective of polariscope test, in lieu of any export tax now required by law: Provided further, That the internal revenue taxes levied by the Colonial Council of Saint Croix, or by the Colonial Council of Saint Thomas and Saint John, in pursuance of the authority granted by this section and sections 1391,¹ 1392, 1394, and 1396 of this title on articles, goods, wares, or merchandise may be levied and collected as the Colonial Council of Saint Croix, or as the Colonial Council of Saint Thomas and Saint John, may direct, on the articles subject to said tax, as soon as the same are manufactured, sold, used, or brought into the island: And provided further, That no discrimination be made between the articles imported from the United States or foreign countries and similar articles produced or manufactured in the municipality of Saint Croix, or in the municipality of Saint Thomas and Saint John, respectively. The officials of the Customs and Postal Services of the United States are directed to assist the appropriate officials of the municipality of Saint Croix, or of the municipality of Saint Thomas and Saint John, in the collection of these taxes.