of those provinces of legislation by plain expression or implication reserved to the States,—such as the regulation of municipal institutions, the punishment of ordinary crimes, the enactment of laws of inheritance and of contract, the erection and maintenance of the common machinery of education, and the control of other such like matters of social economy and every-day administration,—but to check and trim national policy on national questions, to turn Congress back from paths of dangerous encroachment on middle or doubtful grounds of jurisdiction, to keep sharp, when it was like to become dim, the line of demarcation between state and federal privilege, to readjust the weights of jurisdiction whenever either state or federal scale threatened to kick the beam. There never was any great likelihood that the national government would care to take from the States their plainer prerogatives, but there was always a violent probability that it would here and there steal a march over the borders where territory like its own invited it to appropriation; and it was for a mutual defense of such border-land that the two governments were given the right to call a halt upon one another. It was purposed to guard not against revolution, but against unrestrained exercise of questionable powers.
The extent to which the restraining power of
