[T]he constitution controls any legislative act repugnant to it. . . . It is emphatically the province and duty of the judicial department to say wha… - John Marshall

It is emphatically the province and duty of the Judicial Department to say what the law is.

It is emphatically the province and duty of the judicial department to say what the law is. Those who apply the rule to particular cases, must of necessity expound and interpret that rule. If two laws conflict with each other, the courts must decide on the operation of each. So if a law be in opposition to the constitution: if both the law and the constitution apply to a particular case, so that the court must either decide that case conformably to the law, disregarding the constitution; or conformably to the constitution, disregarding the law: the court must determine which of these conflicting rules governs the case. This is of the very essence of judicial duty.

The powers of the legislature are defined, and limited; and that those limits may not be mistaken, or forgotten, the constitution is written. To what purpose are powers limited, and to what purpose is that limitation committed to writing, if these limits may, at any time, be passed by those intended to be restrained? The distinction, between a government with limited and unlimited powers, is abolished, if those limits do not confine the persons on whom they are imposed, and if acts prohibited and acts allowed, are of equal obligation. It is a proposition too plain to be contested, that the constitution controls any legislative act repugnant to it; or, that the legislature may alter the constitution by an ordinary act.

If the States may tax one instrument, employed by the Government in the execution of its powers, they may tax any and every other instrument. They may tax the mail; they may tax the mint; they may tax patent rights; they may tax the papers of the custom house; they may tax judicial process; they may tax all the means employed by the Government to an excess which would defeat all the ends of Government. This was not intended by the American people. They did not design to make their Government dependent on the States. [...] If the controlling power of the States be established, if their supremacy as to taxation be acknowledged, what is to restrain their exercising control in any shape they may please to give it? Their sovereignty is not confined to taxation; that is not the only mode in which it might be displayed. The question is, in truth, a question of supremacy, and if the right of the States to tax the means employed by the General Government be conceded, the declaration that the Constitution and the laws made in pursuance thereof shall be the supreme law of the land is empty and unmeaning declamation.

The acme of judicial distinction means the ability to look a lawyer straight in the eyes for two hours and not hear a damned word he says.