Also known as: duties of tonnage · tonnage duty · tonnage duties · tonnage tax
Written by attorneys · grounded in primary & secondary sources — see below
A tax levied by a state on vessels according to their tonnage or carrying capacity. The Constitution bars states from imposing such a tax without congressional consent.
Duarte Shipping docks its cargo vessels at a state port where the legislature has enacted a per-ton levy to fund harbor maintenance. The company pays under protest and sues, asserting that the charge is a duty of tonnage enacted without congressional approval. The court invalidates the levy because the state lacked the required consent.
Dakota Industries operates tankers that call at ports in a state that obtained explicit congressional authorization before enacting a tonnage-based fee for channel dredging. When the company contests the fee as an unconstitutional duty of tonnage, the court rejects the challenge because Congress had given its consent.
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Duffy Construction charters foreign-flag ships that face a state tonnage duty enacted to match duties imposed abroad on American vessels. The company seeks an injunction, claiming the state acted without congressional consent. The court sustains the injunction because the state lacked authority to impose the duty unilaterally.
Dixon Foods pays a state tax measured by the tonnage of its coastal barges used to transport goods. The company argues the tax is an invalid duty of tonnage. The court upholds the tax after finding it is an income tax rather than a tonnage duty, thereby avoiding the constitutional prohibition.
Diane Dawson’s shipping line faces a state tonnage duty that the President later suspends by proclamation after a foreign nation removes similar charges on U.S. vessels. The company seeks a refund for duties paid before the suspension. The court grants the refund because the presidential action removed the underlying state authority to collect the duty.
The prohibition restricts only the states. Congress retains its own power to lay and collect duties, imposts, and excises, including tonnage-based levies, under its taxing and commerce powers.
Supporting sources
A state may impose a duty of tonnage only with the consent of Congress. Absent that consent, the Constitution forbids the state from laying any such duty.
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Congressional consent removes the dormant Commerce Clause objection. When Congress expressly authorizes states to tax maritime traffic, a facially discriminatory state tonnage tax becomes enforceable provided it does not conflict with specific federal regulations.
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…an exception from the acknowledged power of the States to levy taxes, not from the questionable power to regulate commerce. 'A duty of tonnage' is as much a tax, as a duty on imports or exports; and the reason which induced the prohibition of those taxes, extends to this also. This tax may be imposed by a State, with the consent…