Miranda, the Constitution, and Congress

Are Miranda warnings required by the Constitution, or not? If they are, why has the Supreme Court repeatedly said that the rights created by Miranda are “not themselves rights protected by the Constitution”? If not, why can’t an Act of Congress, such as 18 U.S.C. 3501, declare them to be unnecessary? These were the central questions posed by United States v. Dickerson. It is not clear that the majority opinion ever really answered them. The majority said that “Miranda is constitutionally based,” that Miranda has “constitutional underpinnings,” that Miranda is “a constitutional decision,” and that Miranda “announced a constitutional rule.” But the dissent chided the majority for being unable to bring itself to “come out and say quite clearly: ‘We reaffirm today that custodial interrogation that is not preceded by Miranda warnings or their equivalent violates the Constitution of the United States.'”