Mother May I? Imposing Mandatory Prospective Rules of Statutory Interpretation

May Congress enact laws that instruct courts and other interpreters how to interpret future laws? Although Congress has understood its powers to include such a power, and although a recent article calls for Congress to exercise such a power more extensively than it has, we argue that Congress lacks such a power. Thus, previous exercises of the alleged power, such as the Dictionary Act, are unconstitutional. Moreover, we argue that arguments for such a power premised on the courts' possessing the power to constrain Congress through canons of statutory interpretation rest on an equally dubious foundation: judicial canons of construction that dictate outcomes different from what Congress means those outcomes to be - canons such as the Ashwander canon - are themselves constitutionally infirm. We argue that neither the courts nor Congress through canons or rules of interpretation can legitimately constrain the interpretation of statutes.