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sees fit to leave within his power." Myers v. United States, 272 U.S. 52, 177. The powers of the
President are not as particularized as are those of Congress. But unenumerated powers do not
mean undefined powers. The separation of powers built into our Constitution gives essential
content to undefined provisions in the frame of our government. [Ibid. at 60910.]
Deeply embedded traditional ways of conducting government cannot supplant the
Constitution or legislation, but they give meaning to the words of a text or supply them. It is an
inadmissibly narrow conception of American constitutional law to confine it to the words of the
Constitution and to disregard the gloss which life has written upon them. In short, a systematic,
unbroken, executive practice, long pursued to the knowledge of the Congress and never before
questioned, engaged in by Presidents who have also sworn to uphold the Constitution, making as
it were such exercise of power part of the structure of our government, may be treated as a gloss
on "executive Power" vested in the President by ' 1 of Art. II. [Ibid. at 61011.]
Thus the list of executive assertions of the power of seizure in circumstances comparable to the
present reduces to three in the six-month period from June to December of 1941. We need not
split hairs in comparing those actions to the one before us, though much might be said by way of
differentiation. Without passing on their validity, as we are not called upon to do, it suffices to
say that these three isolated instances do not add up, either in number, scope, duration or
contemporaneous legal justification, to the kind of executive construction of the Constitution
revealed in the Midwest Oil case. Nor do they come to us sanctioned by long-continued
acquiescence of Congress giving decisive weight to a construction by the Executive of its
powers.