1. When the President acts pursuant to an express or implied
authorization of Congress, his authority is at its maximum, for
it includes all that he possesses in his own right plus all that
Congress can delegate. In these circumstances, and in these
only, may he be said (for what it may be worth) to personify the
federal sovereignty. If his act is held unconstitutional under
these circumstances, it usually means that the Federal
Government as an undivided whole lacks power. A seizure executed
by the President pursuant to an Act of Congress would be
supported by the strongest of presumptions and the widest
latitude of judicial interpretation, and the burden of
persuasion would rest heavily upon any who might attack it. 2.
When the President acts in absence of either a congressional
grant or denial of authority, he can only rely upon his own
independent powers, but there is a zone of twilight in which he
and Congress may have concurrent authority, or in which its
distribution is uncertain. Therefore, congressio