rstate
commerce.[320] By a third the business of insurance when transacted
between an insurer and an insured in different States is interstate
commerce.[321]

THE "NECESSARY AND PROPER" CLAUSE

In the majority of the above cases the commerce clause was involved
solely as a limitation on the powers of the States. But when the clause
is treated as a source of national power it is, of course, read in
association with the power of Congress "* * * To make all Laws which
shall be necessary and proper for carrying into Execution the foregoing
Powers, * * *,"[322] with the result that, as is pointed out later,
"interstate commerce" has come in recent years practically to connote
both those operations which precede as well as those which follow
commercial intercourse itself, provided such operations are deemed by
the Court to be capable of "affecting" such intercourse.[323]

"AMONG THE SEVERAL STATES"

In Cohens _v._ Virginia, decided in 1821, Marshall had asserted, "for
all commercial purposes we are one nation."[324] In Gibbons _v._ Ogden,
however, he conceded that the phrase commerce "among the several States"
was "not one which would probably have been selected to indicate the
completely interior traffic of a State"; and added: "The genius and
character of the whole government seem to be, that its action is to be
applied to all external concerns of the nation, and to those internal
concerns which affect the States generally; but not those which are
completely within a particular State, which do not affect other States,
and with which it is not necessary to interfere, for the purpose of
executing some of the general powers of the government."[325]

This recognition of an "exclusively internal" commerce of a State
("intrastate commerce" today) appears at times to have been regarded as
implying the existence of an area of State power which Congress was not
entitled constitutionally to enter.[326] This inference overlooked the
fact that, in consequence of its powers under the necessary and proper
clause, Congress can, as Marshall indicates in the words above quoted,
interfere with the completely internal concerns of a State "for the
purpose of executing its general powers," one of which is its power over
foreign and interstate commerce. It is today established doctrine that
"no form of State activity can constitutionally thwart the regulatory
power granted by the commerce clause to Congress."[327]

And while the word