It is widely regarded as illegitimate for legal systems to retroactively alter the sentences assigned by the courts to offenders once those sentences have become final. Such retroactive changes are deemed to violate ‘fair notice’ requirements and to unreasonably upset the expectations of sentenced offenders. Yet it is important to distinguish retroactive sentencing changes from retroactive changes to legal prohibitions. I contend that the arguments against the former are much less convincing than the arguments against the latter, especially when retroactive sentencing changes would bring sentences more in line with proportionality constraints. The more convincing arguments against retroactive sentencing changes are practical ones; they would upset negotiated pleas and confound the sentencing of repeat and multiple offenders.
Lippke, R. L. (2017). Retroactive Sentencing Changes: Exploring the Complications. Oxford Journal of Legal Studies, gqx017.