MADISONCENTER FOR AMERICAN LEADERSHIP
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The Constitution,
connected.

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The constitutional text

Article I · Section 10

Select any highlighted phrase to understand what it means.

No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility.

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.

No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.

Source: National Constitution Center edition. Original wording is preserved; commentary explains historical and superseded provisions.

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Article I, Section 10, Clause 3a

Tonnage duties require congressional consent

Current text
No State shall, without the Consent of Congress, lay any Duty of Tonnage,

What it means

A state needs Congress’s consent to impose a duty of tonnage, a charge of the constitutionally covered kind on vessels. The historical term commonly concerns burdens associated with a vessel’s carrying capacity or use of a port.

Historical setting

A port state could otherwise raise money from interstate or foreign shipping through charges that functioned like trade barriers. The prohibition complements the national commerce power and restrictions on import duties.

What it does

Not every payment for an actual port service is automatically a prohibited tonnage duty. Distinguishing a genuine service charge from a tax on the vessel or its access is essential.

Debate & interpretation

The consent mechanism allows national judgment about arrangements affecting shared commercial interests. It also recognizes that a charge experienced by ships in one state can affect commerce throughout the Union.

A common misreading

A state cannot evade constitutional scrutiny merely by giving a vessel tax a name other than tonnage.

Think it through

What makes a charge payment for a service rather than a tax for the privilege of entering a port?

Follow the connection

Sources & further reading

Original Madison Center commentary. Explanations distinguish the text, historical context, and interpretive disagreements.

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