Article I, Section 9, of the Constitution includes these words: "No Preference shall be given by any Regulation of Commerce or Revenue to the Ports of one State over those of another." That prohibition is supposed to apply to laws passed by Congress. In 1920, Congress passed the Jones Act, a protectionist law that says all ships transporting goods between U.S. ports must be U.S.-built, U.S.-flagged, U.S.-owned, and U.S.-crewed.

A new lawsuit alleges that the Jones Act violates the port preference clause of the Constitution by putting Hawaiian and Alaskan ports at a disadvantage relative to other states. Since those two ...