The Constitution prohibits the States from making laws on the value and circulation of money: If, notwithstanding this prohibition, a State passes a law of this kind, with which the interested parties refuse to comply because it is contrary to the Constitution, the case must come before a Federal court, because it arises under the laws of the United States. Again, if difficulties arise in the levying of import duties which have been voted by Congress, the Federal court must decide the case, because it arises under the interpretation of a law of the United States. This rule is in perfect accordance with the fundamental principles of the Federal Constitution. The Union, as it was established in 1789, possesses, it is true, a limited supremacy; but it was intended that within its limits it should form one and the same people. *h Within those limits the Union is sovereign. When this point is established and admitted, the inference is easy; for if it be acknowledged that the United States constitute one and the same people within the bounds prescribed by their Constitution, it is impossible to refuse them the rights which belong to other nations. But it has been allowed, from the origin of society, that every nation has the right of deciding by its own courts those questions which concern the execution of its own laws. To this it is answered that the Union is in so singular a position that in relation to some matters it constitutes a people, and that in relation to all the rest it is a nonentity. But the inference to be drawn is, that in the laws relating to these matters the Union possesses all the rights of absolute sovereignty. The difficulty is to know what these matters are; and when once it is resolved (and we have shown how it was resolved, in speaking of the means of determining the jurisdiction of the Federal courts) no further doubt can arise; for as soon as it is established that a suit is Federal—that is to say, that it belongs to the share of sovereignty reserved by the Constitution of the Union—the natural consequence is that it should come within the jurisdiction of a Federal court. h [ This principle was in some measure restricted by the introduction of the several States as independent powers into the Senate, and by allowing them to vote separately in the House of Representatives when the President is elected by that body. But these are exceptions, and the contrary principle is the rule.]