Article III, Section 2, Clause 1:
The Judicial Power shall extend to all Cases, in Law and Equity, arising under this Constitution, the Laws of the United States, and Treaties made, or which shall be made, under their Authority;—to all Cases affecting Ambassadors, other public Ministers and Consuls;—to all Cases of admiralty and maritime Jurisdiction; to Controversies to which the United States shall be a Party;—to Controversies between two or more States; between a State and Citizens of another State; between Citizens of different States,—between Citizens of the same State claiming Lands under Grants of different States, and between a State, or the Citizens thereof, and foreign States, Citizens or Subjects.
A precautionary rule early formulated and at the base of the traditional concept of judicial restraint was expressed by Professor James Bradley Thayer to the effect that a statute could be voided as unconstitutional only "when those who have the right to make laws have not merely made a mistake, but have made a very clear one, – so clear that it is not open to rational question." 1 Whether phrased this way or phrased so that a statute is not to be voided unless it is unconstitutional beyond all reasonable doubt, the rule is of ancient origin 2 and of modern adherence. 3 In operation, however, the rule is subject to two influences, which seriously impair its efficacy as a limitation. First, the conclusion that there has been a clear mistake or that there is no reasonable doubt is that drawn by five Justices if a full Court sits. If five Justices of learning and detachment to the Constitution are convinced that a statute is invalid and if four others of equal learning and attachment are convinced it is valid, the convictions of the five prevail over the convictions or doubts of the four. Second, the Court has at times made exceptions to the rule in certain categories of cases. Statutory interferences with "liberty of contract" were once presumed to be unconstitutional until proved to be valid; 4 more recently, presumptions of invalidity have expressly or impliedly been applied against statutes alleged to interfere with freedom of expression and of religious freedom, which have been said to occupy a "preferred position" in the constitutional scheme of things. 5