Section 10, Clause 2
Clause 1. Treaties, Coining Money, Impairing Contracts
Clause 2. Duties on Exports and Imports
Clause 3. Tonnage Duties and Interstate Compacts
Clause 2. Duties On Exports and Imports
No State shall, without the Consent of the Congress, lay any Imposts or Duties on Imports or Exports, except what may be absolutely necessary for executing it’s inspection Laws: and the net Produce of all Duties and Imposts, laid by any State on Imports or Exports, shall be for the Use of the Treasury of the United States; and all such Laws shall be subject to the Revision and Controul of the Congress.