Congress, in response, enacted § 3501. That statute clearly was designed to overrule "Miranda" because it expressly focused solely on voluntariness of the confession as a touchstone for admissibility. Did Congress have the authority to pass such a law? On the one hand, the Court's power to craft nonconstitutional supervisory rules over the federal courts exists only in the absence of a specific statute passed by Congress. However, if on the other hand the "Miranda" rule was constitutional, Congress could not overrule it, because the Court alone is the final arbiter of what the Constitution requires. As evidence of the fact that the "Miranda" rule was constitutional in nature, the Court pointed out that many of its subsequent decisions applying and limiting the requirement arose in decisions from state courts, over which the Court lacked the power to impose supervisory nonconstitutional rules. Furthermore, although the Court had previously invited legislative involvement in the effort to devise prophylactic measures for protecting criminal defendants against overbearing tactics of the police, it had consistently held that these measures must not take away from the protections "Miranda" had afforded.