Lex mitior

I'm attending a fascinating conference on criminal law in Sao Paolo, Brazil, organized by the Instituto  Brasileiro de Ciéncias Criminais. This morning, Prof. Sandra Babcock of Northwestern University delivered a fabulous lecture on capital punishment. I learned that the death penalty had been abolished recently in New Mexico, but that the governor had refused to let the legislation be retroactive. In other words, henceforth persons convicted cannot be sentenced to death, but the sentence stands for those already sentenced to death.
The United States is a party to the International Covenant on Civil and Political Rights. Article 15(1) of the Covenant declares:
No one shall be held guilty of any criminal offence on account of any act or omission which did not constitute a criminal offence, under national or international law, at the time when it was committed. Nor shall a heavier penalty be imposed than the one that was applicable at the time when the criminal offence was committed. If, subsequent to the commission of the offence, provision is made by law for the imposition of the lighter penalty, the offender shall benefit thereby. (my italics)
Article 15 is a non-derogable provision. At the time of ratification, the United States made no reservation to article 15. So it seems to me that the policy proposed by the governor is in violation of the international obligations of the United States. Perhaps France, Japan or Cameroon will remind the United States of this issue during the universal periodic review in November.
The principle by which a person is to benefit from the lighter penalty where there has been a change in the law is known by the Latin phrase lex mitior. There is a fascinating recent decision of the European Court of Human Rights on this issue: Scoppola v. Italy (No. 2).  In the past, the Strasbourg caselaw had always held that lex mitior did not exist under the European Convention on Human Rights because there is no provision comparable to the last sentence of article 15(1) of the International Covenant. But the Grand Chamber of the Court reversed that position, holding that despite the silence of the Convention, the norm must be interpreted as being comprised within the Convention.
The Court based its change in approach on the fact that 'a consensus has gradually emerged in Europe and internationally around the view that application of a criminal law providing for a more lenient penalty, even one enacted after the commission of the offence, has become a fundamental principle of criminal law' (para. 109). The Court conceded that article 7 of the Convention'does not expressly mention' such an obligation.

According to the Grand Chamber:

 

108. In the Court's opinion, it is consistent with the principle of the rule of law, of which Article 7 forms an essential part, to expect a trial court to apply to each punishable act the penalty which the legislator considers proportionate. Inflicting a heavier penalty for the sole reason that it was prescribed at the time of the commission of the offence would mean applying to the defendant's detriment the rules governing the succession of criminal laws in time. In addition, it would amount to disregarding any legislative change favourable to the accused which might have come in before the conviction and continuing to impose penalties which the State – and the community it represents – now consider excessive. The Court notes that the obligation to apply, from among several criminal laws, the one whose provisions are the most favourable to the accused is a clarification of the rules on the succession of criminal laws, which is in accord with another essential element of Article 7, namely the foreseeability of penalties.

109, In the light of the foregoing considerations, the Court takes the view that it is necessary to depart from the case-law established by the Commission in the case of X v. Germany and affirm that Article 7 § 1 of the Convention guarantees not only the principle of non-retrospectiveness of more stringent criminal laws but also, and implicitly, the principle of retrospectiveness of the more lenient criminal law.

This must be a further shock to those who don't appreciate judicial lawmaking. Personally, I like it.