Proportionality of penalties as a fundamental right?

Proportionality in criminal law is usually discussed in relationship to criminalization or as a criterion for the judicial determination of the penalty. This paper asks to what extent proportionality of the penalty can also work as an individual fundamental (or human) right, based on domestic Constitutions or international human rights instruments.
As a fundamental right, proportionality of penalties operates in two directions. On the one hand, it is a limit to judicial discretion in the determination of the penalty. On the other hand, it can be conceived as a limit to legislative discretion in setting the appropriate sentencing framework for an offence. Thus, criminal laws providing for disproportionate sentencing frameworks could be declared void or held incompatible with human rights standards, in as far as they can lead to the imposition of such sentences.
These two basic functions are discussed in the light of the most recent case law of the Italian Constitutional Court.