[T]he Government of the Union, though limited in its powers, is supreme within its sphere of action. This would seem to result necessarily from its n… - John Marshall

It is incidental to, and is implied in the several acts by which these institutions are created, and is secured to the individuals employed in them, by the judicial power alone; that is, the judicial power is the instrument employed by the government in administering this security. That department has no will, in any case. If the sound construction of the act be, that it exempts the trade of the Bank, as being essential to the character of a machine necessary to the fiscal operations of the government, from the control of the States, Courts are as much bound to give it that construction, as if the exemption had been established in express terms. Judicial power, as contradistinguished from the power of the laws, has no existence. Courts are the mere instruments of the law, and can will nothing. When they are said to exercise a discretion, it is a mere legal discretion, a discretion to be exercised in discerning the course prescribed by law; and, when that is discerned, it is the duty of the Court to follow it. Judicial power is never exercised for the purpose of giving effect to the will of the Judge; always for the purpose of giving effect to the will of the Legislature; or, in other words, to the will of the law.

Whether a law be void for its repugnancy to the Constitution, is, at all times, a question of much delicacy, which out seldom, if ever, to be decided in the affirmative, in doubtful case. … But it is not on slight implication and vague conjecture that the legislature is to be pronounced to have transcended its powers, and its acts to be considered as void. The opposition between the Constitution and the law should be such that the judge feels a clear and strong conviction of their incompatibility with each other.

In America, the powers of sovereignty are divided between the Government of the Union and those of the States. They are each sovereign with respect to the objects committed to it, and neither sovereign with respect to the objects committed to the other. We cannot comprehend that train of reasoning, which would maintain that the extent of power granted by the people is to be ascertained not by the nature and terms of the grant, but by its date. Some State Constitutions were formed before, some since, that of the United States. We cannot believe that their relation to each other is in any degree dependent upon this circumstance. Their respective powers must, we think, be precisely the same as if they had been formed at the same time. Had they been formed at the same time, and had the people conferred on the General Government the power contained in the Constitution, and on the States the whole residuum of power, would it have been asserted that the Government of the Union was not sovereign, with respect to those objects which were intrusted to it, in relation to which its laws were declared to be supreme? If this could not have been asserted, we cannot well comprehend the process of reasoning which maintains that a power appertaining to sovereignty cannot be connected with that vast portion of it which is granted to the General Government, so far as it is calculated to subserve the legitimate objects of that Government.