In this situation judicial review as exercised by the Supreme Court does
not cease being an important technique of government under the
Constitution, but its field of operation has contracted. The purpose
which it serves more and more exclusively is the purpose for which it
was originally created to serve, the maintenance of the principle of
National Supremacy. But in fact, this is the purpose which it has always
served predominantly, even in the era when it was cutting its widest
swathe in the field of national legislative policy, the period from 1895
to 1935. Even then there was a multiplicity of state legislatures and
only one Congress, so that the legislative grist that found its way to
the Court's mill was overwhelmingly of local provenience. And since then
several things have happened to confirm this predominance: first, the
annexation to Amendment XIV of much of the content of the Federal Bill
of Rights; secondly, the extension of national legislative power,
especially along the route of the commerce clause, into the field of
industrial regulation, with the result of touching state legislative
power on many more fronts than ever before; thirdly, the integration of
the Nation's industrial life, which has brought to the National
Government a major responsibility for the maintenance of a functioning
social order.

Forty years ago the late Justice Holmes said:

"I do not think the United States would come to an end if we
[the Court] lost our power to declare an Act of Congress void.
I do think the Union would be imperiled if we could not make
that declaration as to the laws of the several States".[78]

By and large, this still sizes up the situation.