Taxes and assessments on property and incomes, internal-revenue taxes, license fees, and service fees may be imposed and collected, and royalties for franchises, privileges, and concessions granted may be collected for the purposes of the Government of the Virgin Islands as may be provided and defined by the municipal councils herein established: Provided, That all money hereafter derived from any tax levied or assessed for a special purpose shall be treated as a special fund in the treasury of the Virgin Islands and paid out for such purpose only, except when otherwise authorized by the legislative authority having jurisdiction after the purpose for which such fund was created has been accomplished. Until Congress shall otherwise provide, all laws concerning import duties and customs in the municipality of Saint Thomas and Saint John now in effect shall be in force and effect in and for the Virgin Islands: Provided, That the Secretary of the Treasury shall designate the several ports and sub-ports of entry in the Virgin Islands of the United States and shall make such rules and regulations and appoint such officers and employees as he may deem necessary for the administration of the customs laws in the Virgin Islands of the United States; and he shall fix the compensation of all such officers and employees and provide for the payment of such compensations and other expenses of the collection of duties, fees, and taxes imposed under the customs laws from the receipts thereof. The export duties in effect on June 22, 1936 may be from time to time reduced, repealed, or restored by ordinance of the municipal council having jurisdiction: Provided further, That no new export duties shall be levied in the Virgin Islands except by the Congress.