141. The line of demarcation between powers delegated and powers reserved has always been, and doubtless always will be, in dispute. The question involved is political as well as constitutional. The abolition of slavery by the Thirteenth Amendment excludes pro-slavery legislation of any kind affecting the United States or any place subject to its jurisdiction. In like manner the Fourteenth Amendment forbids Congress, or any State, to assume or pay any debt, or obligation incurred in aid of insurrection or rebellion against the United States, or any claim for the loss or emancipation of any slave. All these limitations of legislative power are practical guides and measurements by which the judicial power,—the law courts,—can determine what the law is, whether the act of Congress conflicts with the Constitution. It is largely through these expressed limitations that the judiciary becomes a check on the legislative.[381] 142. The limitations of the powers of the States are numerous and specific. As to limitations of State power (_i. e._, the power of the State government, executive, legislative, judicial, administrative), within State jurisdiction, the several State constitutions alone are authoritative and final.[382] The Union is an indestructible Union of indestructible States, yet the States composing the Union are under limitations as members of that Union. Except as to the places of choosing senators, Congress may at any time prescribe the times, places, and manner of holding elections of senators and representatives.[383] Congress has exclusive jurisdiction over the District of Columbia, and over places purchased from any State, and over federal property.[384] But the Constitution enumerates limitations of the States, each of which eliminates sovereignty from the State and all together, with some other limitations, reduce a State to what Hamilton, in _The Federalist_ calls “residuary sovereignty.”[385] No State shall enter into any treaty, alliance, or confederation; grant letters of marque or reprisal; coin money; emit bills of credit; make anything but gold and silver coin a tender in payment of debts; pass any bill of attainder, _ex post facto_, law, or law impairing the obligation of contracts, or grant any title of nobility.[386] These limitations are of power usually classed as sovereign. Of similar scope are the limitations, prescribed by the Constitution, of State power of taxation,—that is, of laying imposts or duties; of keeping troops or ships of war; of entering into any agreement with another State, or with a foreign power; of engaging in war, unless actually invaded, or in imminent danger of invasion, not admitting of delay. None of these powers can a State in the Union exercise without the consent of Congress.[387]