The fourth period is still with us. It was ushered in by World War I, but its results were consolidated and extended during the 1930's, and have been subsequently still further enlarged and confirmed by World War II and the "cold war". Many of these results have been treated above. Others can be searched out in the pages of this volume. What they sum up to is this: that what was once vaunted as a Constitution of Rights, both State rights and private rights, has been replaced to a great extent by a Constitution of Powers. The Federal System has shifted base in the direction of a consolidated national power; within the National Government itself there has been an increased flow of power in the direction of the President; even judicial enforcement of the Bill of Rights has faltered at times, in the presence of national emergency.
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: