Section 10 of Article I of the U.S. Constitution authorizes each state to enter into an “agreement or compact with another state” with the consent of Congress, but contains no reference to whether the United States may be a party to such a compact. James Madison in The Federalist No. 44 quoted the last two clauses of the section that include the compact provision, focused on the prohibition of state import and export duties, and added “[the] remaining particulars of this clause fall within reasons which are either so obvious, or have been so fully developed, that they may be passed over without remark.” 1
The section does not specify the process by which states may enter into compacts or make a distinction between an agreement and a compact. It appears the two terms were used interchangeably and could include agreements and compacts entered into by either state legislatures or state administrative officers. Chief Justice Roger Taney of the U.S. Supreme Court in 1840 concluded the term “agreement” referred to a verbal understanding. 2 The court in 1893 commented on the two terms as follows:
Compacts or agreements—and we do not perceive any difference in the meaning, except that the word “compact” is generally used with reference to more formal and serious engagements than is usually implied in the term “agreement”—cover all stipulations affecting the conduct or claims of the parties. 3
It has become established, however, that agreements entered into by administrators of sister states do not require the consent of Congress to be effective.
The progenitors of the interstate compact were court decisions and nine