Where it was deemed expedient particular rights of the States were expressly guaranteed by the Constitution, but in all things besides these rights were guarded by the limitation of the powers granted and by express reservation of all powers not granted in the compact of union. Thus the great power of taxation was limited to purposes of common defense and general welfare, excluding objects appertaining to the local legislation of the several States; and those purposes of general welfare and common defense were afterwards defined by specific enumeration as being matters only of co-relation between the States themselves or between them and foreign governments, which, because of their common and general nature, could not be left to the separate control of each State.
Of the circumstances of local condition, interest, and rights in which a portion of the States, constituting one great section of the Union, differed from the rest and from another section, the most important was the peculiarity of a larger relative colored population in the Southern than in the Northern States.
A population of this class, held in subjection, existed in nearly all the States, but was more numerous and of more serious concernment in the South than in the North on account of natural differences of climate and production; and it was foreseen that, for the same reasons, while this population would diminish and sooner or later cease to exist in some States, it might increase in others. The peculiar character and magnitude of this question of local rights, not in material relations only, but still more in social ones, caused it to enter into the special stipulations of the Constitution.