ty.[1780] The framers of the Constitution went further. By the first
clause of this section they laid down an unqualified prohibition against
"any treaty, alliance or confederation"; and by the third clause they
required the consent of Congress for "any agreement or compact." The
significance of this distinction was pointed out by Chief Justice Taney
in Holmes _v._ Jennison.[1781] "As these words ('agreement or compact')
could not have been idly or superfluously used by the framers of the
Constitution, they cannot be construed to mean the same thing with the
word treaty. They evidently mean something more, and were designed to
make the prohibition more comprehensive. * * * The word 'agreement,'
does not necessarily import and direct any express stipulation; nor is
it necessary that it should be in writing. If there is a verbal
understanding, to which both parties have assented, and upon which both
are acting, it is an 'agreement.' And the use of all of these terms,
'treaty,' 'agreement,' 'compact,' show that it was the intention of the
framers of the Constitution to use the broadest and most comprehensive
terms; and that they anxiously desired to cut off all connection or
communication between a State and a foreign power; and we shall fail to
execute that evident intention, unless we give to the word 'agreement'
its most extended signification; and so apply it as to prohibit every
agreement, written or verbal, formal or informal, positive or implied,
by the mutual understanding of the parties."[1782] But in Virginia _v._
Tennessee,[1783] decided more than a half century later, the Court
shifted position, holding that the unqualified prohibition of compacts
and agreements between States without the consent of Congress did not
apply to agreements concerning such minor matters as adjustments of
boundaries, which have no tendency to increase the political powers of
the contractant States or to encroach upon the just supremacy of the
United States. This divergence of doctrine may conceivably have
interesting consequences.[1784]

Subject Matter of Interstate Compacts

For many years after the Constitution was adopted, boundary disputes
continued to predominate as the subject matter of agreements among the
States. Since the turn of the twentieth century, however, the interstate
compact has been used to an increasing extent as an instrument for State
cooperation in carrying out affirmative programs for solving common
problem