_It is emphatically the province and duty of the judicial department to say what the law is._[272] In these words is stated the essential doctrine of judicial supremacy. As the doctrine is fundamental, the reason for it is essential to a proper understanding of its vast import: That the people have an original right to establish for their future government such principles as in their opinion shall most conduce to their own happiness, is the basis on which the whole American fabric has been erected. The exercise of this original right is a very great exertion; nor can it, nor ought it to be frequently repeated. The principles, therefore, so established are deemed fundamental. And as the authority from which they proceed is supreme, and can seldom act, they are designed to be permanent. This original and supreme will organizes the government, and assigns to different departments their respective powers. It may either stop here or establish certain limits not to be transcended by those departments.... 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. Between these alternatives there is no middle ground. The Constitution is either a superior, paramount law, unchangeable by ordinary means, or it is on a level with ordinary legislative acts and, like other acts, is alterable when the legislature shall please to alter it. If the former part of the alternative be true, then a legislative act contrary to the Constitution is not law; if the latter part be true, then written constitutions are absurd attempts on the part of the people to limit a power in its own nature illimitable. Certainly all those who have framed written constitutions contemplate them as forming a fundamental and paramount law of the nation, and consequently the theory of every such government must be, that an act of the Legislature repugnant to the constitution is void.... 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 the 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.... Those, then, who controvert the principle that the Constitution is to be considered in court as a paramount law, are reduced to the necessity of maintaining that courts must close their eyes on the Constitution, and see only the law.