the negotiation of a
treaty, and the _modus vivendi_, which is designed to serve as a
temporary substitute for one. Executive agreements become of
constitutional significance when they constitute a determinative factor
of future foreign policy and hence of the country's destiny. Within
recent decades, in consequence particularly of our participation in
World War II and our immersion in the conditions of international
tension which have prevailed both before and after this war, Presidents
have entered into agreements with other governments some of which have
approximated temporary alliances. It cannot be justly said, however,
that in so doing they have acted without considerable support from
precedent.

LAW-MAKING EXECUTIVE AGREEMENTS

An early instance of executive treaty-making was the agreement by which
President Monroe in 1817 brought about a delimitation of armaments on
the Great Lakes. The arrangement was effected by an exchange of notes,
which nearly a year later was laid before the Senate with a query as to
whether it was within the President's power, or whether advice and
consent of the Senate were required. The Senate approved the agreement
by the required two-thirds vote, and it was forthwith proclaimed by the
President without there having been a formal exchange of
ratifications.[225] Of a kindred type, and owing much to the President's
capacity as Commander in Chief, was a series of agreements entered into
with Mexico between 1882 and 1896 according each country the right to
pursue marauding Indians across the common border.[226] Commenting on
such an agreement, the Court remarked, a bit uncertainly: "While no act
of Congress authorizes the executive department to permit the
introduction of foreign troops, the power to give such permission
without legislative assent was probably assumed to exist from the
authority of the President as commander in chief of the military and
naval forces of the United States. It may be doubted, however, whether
such power could be extended to the apprehension of deserters [from
foreign vessels] in the absence of positive legislation to that
effect."[227] Justice Gray and three other Justices were of the opinion
that such action by the President must rest upon express treaty or
statute.[228]

PRESIDENT McKINLEY'S CONTRIBUTION

Notable expansion of Presidential power in this field first became
manifest in the administration of President McKinley. At the outset of
war wi