Federal judges, when interpreting the Constitution, frequently use The Federalist Papers as a contemporary account of the intentions of the framers and ratifiers. They have been applied on issues ranging from the power of the federal government in foreign affairs (in Hines v. Davidowitz) to the validity of ex post facto laws (in the 1798 decision Calder v. Bull, apparently the first decision to mention The Federalist). By 2000, The Federalist had been quoted 291 times in Supreme Court decisions.
The amount of deference that should be given to The Federalist Papers in constitutional interpretation has always been somewhat controversial. As early as 1819, Chief Justice John Marshall noted in the famous case McCulloch v. Maryland, that "the opinions expressed by the authors of that work have been justly supposed to be entitled to great respect in expounding the Constitution. No tribute can be paid to them which exceeds their merit; but in applying their opinions to the cases which may arise in the progress of our government, a right to judge of their correctness must be retained." Madison believed The Federalist Papers were the ideas of the Founders and not just mere expressions. In a letter to Thomas Ritchie in 1821, he stated that "the legitimate meaning of the Instrument must be derived from the text itself; or if a key is to be sought elsewhere, it must be not in the opinions or intentions of the Body which planned & proposed the Constitution, but in the sense attached to it by the people in their respective State Conventions where it recd. all the authority which it possesses."