It's from here:
Safeguards Guaranteeing Protection of the Rights of those Facing the Death Penalty
Economic and Social Council resolution 1984/50, adopted 25 May 1984
which can be read with other useful stuff here:
http://www.uncjin.org/Standards/UNRules.pdfThere's also this, at the international law level, in the International Covenant on Civil and Political Rights:
http://www.unhchr.ch/html/menu3/b/a_ccpr.htmArticle 6
1. Every human being has the inherent right to life. This right shall be protected by law. No one shall be arbitrarily deprived of his life.
2. In countries which have not abolished the death penalty, sentence of death may be imposed only for the most serious crimes in accordance with the law in force at the time of the commission of the crime and not contrary to the provisions of the present Covenant and to the Convention on the Prevention and Punishment of the Crime of Genocide. This penalty can only be carried out pursuant to a final judgement rendered by a competent court.
3. When deprivation of life constitutes the crime of genocide, it is understood that nothing in this article shall authorize any State Party to the present Covenant to derogate in any way from any obligation assumed under the provisions of the Convention on the Prevention and Punishment of the Crime of Genocide.
4. Anyone sentenced to death shall have the right to seek pardon or commutation of the sentence. Amnesty, pardon or commutation of the sentence of death may be granted in all cases.
5. Sentence of death shall not be imposed for crimes committed by persons below eighteen years of age and shall not be carried out on pregnant women.
6. Nothing in this article shall be invoked to delay or to prevent the abolition of capital punishment by any State Party to the present Covenant.
(The US has ratified that covenant.)
The idea behind these rules is not that capital punishment can be a good thing -- it is that the international community has no authority over whether an individual state uses capital punishment, but attempts to get those states that do, to adhere to a minimum set of rules for the application of it.
Those rules are "naïve" in the same sense as any other international treaty of this nature is -- the only real guarantee of them being followed is the good will of the states that sign them.
The second optional protocol to that Covenant says:
http://193.194.138.190/html/menu3/b/a_opt2.htmSecond Optional Protocol to the International Covenant on Civil and Political Rights, aiming at the abolition of the death penalty
The States Parties to the present Protocol,
Believing that abolition of the death penalty contributes to enhancement of human dignity and progressive development of human rights,
Recalling article 3 of the Universal Declaration of Human Rights, adopted on 10 December 1948, and article 6 of the International Covenant on Civil and Political Rights, adopted on 16 December 1966,
Noting that article 6 of the International Covenant on Civil and Political Rights refers to abolition of the death penalty in terms that strongly suggest that abolition is desirable,
Convinced that all measures of abolition of the death penalty should be considered as progress in the enjoyment of the right to life,
Desirous to undertake hereby an international commitment to abolish the death penalty,
Have agreed as follows:
Article 1
1. No one within the jurisdiction of a State Party to the present Protocol shall be executed.
2. Each State Party shall take all necessary measures to abolish the death penalty within its jurisdiction. ...
I assume the US has not ratified that one.
Lots of info about the death penalty at the international level here:
http://web.amnesty.org/library/Index/ENGACT500022003?open&of=ENG-USAThe Innocence Project is here:
http://www.innocenceproject.org/.