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.Marbury v. Madison
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.
The Very Essence of Judicial Duty