so far as to prevent or obstruct other classes of persons from
the right to hold personal and commercial intercourse with the people of
the United States."[778]

STATE QUARANTINE LAWS

On the other hand, it has been repeatedly held that the States may, in
the absence of legislation by Congress, enact quarantine laws, even
though in effect they thereby regulate foreign commerce; and furthermore
that such legislation may be, in the interest of effective enforcement,
applied beyond the mere exclusion of diseased persons. Thus in the
leading case the State of Louisiana was sustained in authorizing its
Board of Health in its discretion to prohibit the introduction into any
infected portion of the State of "persons acclimated, unacclimated or
said to be immune, when in its judgment the introduction of such persons
would add to or increase the prevalence of the disease."[779] At the
same time it was emphasized that all such legislation was subject to be
supplanted by Congress at any time.

STATE GAME PROTECTION AND FOREIGN COMMERCE

The Court's tolerance of legal provisions which might not standing alone
be constitutional, when they are designed to make legislation within the
police power practically enforceable, is also illustrated in connection
with State game laws. In the case of Silz _v._ Hesterberg[780] the Court
was confronted with a New York statute establishing a closed season for
certain game, during which season it was a penal offense to take or
possess any of the protected animals, fish or birds; and providing
farther that the ban should equally apply "to such fish, game or flesh
coming from without the State as to that taken within the State." This
provision was held to have been validly applied in the case of a dealer
in imported game who had in his possession during the closed season "one
dead body of an imported grouse, ..., and taken in Russia." Again the
absence of conflicting legislation by Congress was adverted to.[781]

The Police Power and Interstate Commerce

GENERAL PRINCIPLES

In Southern Pacific Co. _v._ Arizona,[782] decided in 1945, Chief
Justice Stone made the following systematic statement of principles
which have guided the Court in the exercise of its power of judicial
review of State legislation affecting interstate commerce: "Although the
commerce clause conferred on the national government power to regulate
commerce, its possession of the power does not exclude all state power