Article 1, Section 9:
"No Preference shall be given by any Regulation of Commerce or Revenue to the Ports of one State over those of another"
Congress cannot tax all Americans to fund pork projects in the districts or with the friends of powerful members of Congress.
Because of repeated efforts by the powerful Senator Henry Clay to tax all Americans to fund pork highway projects in Kentucky, the Confederate States of America moved the "post Roads" and "No Preference" clauses into their Commerce Clause.
Constitution of the Confederate States, March 11, 1861:
"Sec. 8. The Congress shall have power-
(3) To regulate commerce with foreign nations, and among the several States, and with the Indian tribes; but neither this, nor any other clause contained in the Constitution, shall ever be construed to delegate the power to Congress to appropriate money for any internal improvement intended to facilitate commerce; except for the purpose of furnishing lights, beacons, and buoys, and other aids to navigation upon the coasts, and the improvement of harbors and the removing of obstructions in river navigation; in all which cases such duties shall be laid on the navigation facilitated thereby as may be necessary to pay the costs and expenses thereof."