But, Sir, the people have wisely provided, in the Constitution itself, a proper, suitable mode and tribunal for settling questions of constitutional law. There are in the Constitution grants of powers to Congress, and restrictions on these powers. There are, also, prohibitions on the States. Some authority must, therefore, necessarily exist, having the ultimate jurisdiction to fix and ascertain the interpretation of these grants, restrictions, and prohibitions. The Constitution has itself pointed out, ordained, and established that authority. How has it accomplished this great and essential end? By declaring, Sir, that "_the Constitution, and the laws of the United States made in pursuance thereof, shall be the supreme law of the land, anything in the constitution or laws of any State to the contrary notwithstanding_." This, Sir, was the first great step. By this the supremacy of the Constitution and laws of the United States is declared. The people so will it. No State law is to be valid which comes in conflict with the Constitution, or any law of the United States passed in pursuance of it. But who shall decide this question of interference? To whom lies the last appeal? This, Sir, the Constitution itself decides also, 25 by declaring, "_that the judicial power shall extend to all cases arising under the Constitution and laws of the United States_." These two provisions cover the whole ground. They are, in truth, the keystone of the arch! With these it is a government; without them it is a confederation. In pursuance of these clear and express provisions, Congress established, at its very first session, in the judicial act, a mode for carrying them into full effect, and for bringing all questions of constitutional power to the final decision of the Supreme Court. It then, Sir, became a government. It then had the means of self-protection; and but for this, it would, in all probability, have been now among things which are past. Having constituted the government, and declared its powers, the people have further said, that, since somebody must decide on the extent of these powers, the government shall itself decide; subject, always, like other popular governments, to its responsibility to the people. And now, Sir, I repeat, how is it that a State legislature acquires any power to interfere? Who, or what, gives them the right to say to the people, "We, who are your agents and servants for one purpose, will undertake to decide, that your other agents and servants, appointed by you for another purpose, have transcended the authority you gave them!" The reply would be, I think, not impertinent, "Who made you a judge over another's servants? To their own masters they stand or fall."