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 discr… - John Marshall

An unlimited power to tax involves, necessarily, a power to destroy; because there is a limit beyond which no institution and no property can bear taxation. A question of constitutional power can hardly be made to depend on a question of more or less. If the states may tax, they have no limit but their discretion; and the bank, therefore, must depend on the discretion of the state governments for its existence. This consequence is inevitable. The object in laying this tax, may have been revenue to the state. In the next case, the object may be to expel the bank from the state; but how is this object to be ascertained, or who is to judge of the motives of legislative acts?

[T]he power of creating a corporation is one appertaining to sovereignty, and is not expressly conferred on Congress. This is true. But all legislative powers appertain to sovereignty. The original power of giving the law on any subject whatever is a sovereign power, and if the Government of the Union is restrained from creating a corporation as a means for performing its functions, on the single reason that the creation of a corporation is an act of sovereignty, if the sufficiency of this reason be acknowledged, there would be some difficulty in sustaining the authority of Congress to pass other laws for the accomplishment of the same objects. The Government which has a right to do an act and has imposed on it the duty of performing that act must, according to the dictates of reason, be allowed to select the means, and those who contend that it may not select any appropriate means that one particular mode of effecting the object is excepted take upon themselves the burden of establishing that exception. [...] The power of creating a corporation, though appertaining to sovereignty, is not, like the power of making war or levying taxes or of regulating commerce, a great substantive and independent power which cannot be implied as incidental to other powers or used as a means of executing them. It is never the end for which other powers are exercised, but a means by which other objects are accomplished. No contributions are made to charity for the sake of an incorporation, but a corporation is created to administer the charity; no seminary of learning is instituted in order to be incorporated, but the corporate character is conferred to subserve the purposes of education. No city was ever built with the sole object of being incorporated, but is incorporated as affording the best means of being well governed. The power of creating a corporation is never used for its own sake, but for the purpose of effecting something else. No sufficient reason is therefore perceived why it may not pass as incidental to those powers which are expressly given if it be a direct mode of executing them.

[..] it can scarcely be necessary to say that the existence of State banks can have no possible influence on the question. No trace is to be found in the Constitution of an intention to create a dependence of the Government of the Union on those of the States, for the execution of the great powers assigned to it. Its means are adequate to its ends, and on those means alone was it expected to rely for the accomplishment of its ends. To impose on it the necessity of resorting to means which it cannot control, which another Government may furnish or withhold, would render its course precarious, the result of its measures uncertain, and create a dependence on other Governments which might disappoint its most important designs, and is incompatible with the language of the Constitution. But were it otherwise, the choice of means implies a right to choose a national bank in preference to State banks, and Congress alone can make the election. After the most deliberate consideration, it is the unanimous and decided opinion of this Court that the act to incorporate the Bank of the United States is a law made in pursuance of the Constitution, and is a part of the supreme law of the land.