While statutes determine the conditions under which an individual is to be held accountable for their actions and identifies the punishment that shall attach to that conduct, they are not engraved in stone. Laws can and are changed. Legislatures will revisit whether a penalty is too harsh (or too lenient), and amend an existing statute to reflect the legislature’s evaluation of what is contemporaneously appropriate. This re-evaluation of a statutory punishment is ongoing assessment to determine whether the punishment is proportional to the conduct. Blanket retroactive amelioration allows society to correct overly harsh, overreactions and to restore the balance between the punishment and the offense. No theory is perfect but it would seem a rather distasteful system of criminal justice and one that is manifestly unjust if punishments are lessened or conduct is decriminalized and not retroactively applied. Mercy and justice should not be sacrificed for adherence to a process.
S. David Mitchell, Blanket Retroactive Amelioration: a Remedy for Disproportionate Punishments, 40 Fordham Urb.L.J. City Square 14 (2013)