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.

Larry Alexander & Saikrishna Prakash, Mother May I? Imposing Mandatory Prospective Rules of Statutory Interpretation, 20 Constitutional Commentary 97–110 (2004).
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