The question is about the qualifying of (non-)compliance in context of the duties arising from a treaty-like foundational legal instrument under public international law, the interaction between the binding nature of the U.N. Charter and further instruments and their interpretation and structure, and, incidentally, associated trends in the field of human rights.
Universal Declaration of Human Rights
When the foundational Universal Declaration of Human Rights (UDHR) (part of the International Bill of Human Rights), detailing the rights and freedoms stated in the binding United Nations Charter, was adopted in 1948 (despite some constructive criticism, see also Wikipedia), Saudi Arabia was the only country with a Muslim population which abstained (furthermore it neither signed the International Covenant on Civil and Political Rights nor the International Covenant on Economic, Social and Cultural Rights, contrary to many countries with a Muslim population like Iran.). That abstention was construed as resulting from "the wording of Article 16 on equal marriage rights and because of objections to the clause in Article 18 which states that everyone has the right "to change his religion or belief""; more generally it claimed it violated Sharia law, yet René Cassin (who prepared the second draft of the UHDR based on a first draft by John Peters Humphrey, OC) noted that "the inclusion of Article 18 had not prevented other countries with Muslim populations, like Syria, Iran, Turkey and Pakistan, from voting for the Declaration." (René Cassin, 1958. Republished in Cassin, René, La Pensée et l'action (Paris, Lalou, 1972), p. 108).
In 1968, the United Nations International Conference on Human Rights explains the Declaration "constitutes an obligation for the members of the international community" to all persons (Wikipedia). I share the opinion that furthermore the Declaration forms part customary international law. In 1982, now that WWII had been over for a quarter of a century, Iran, despite having voted for the UDHR in 1948 claimed that the Declaration was ""a secular understanding of the Judeo-Christian tradition" which could not be implemented by Muslims without conflict with Sharia" (Iranian representative to the U.N.'s quote on Wikipedia).
Cairo Declaration on Human Rights in Islam, Arab Charter on Human Rights
In 1990 the then 45 member states of the Organization of Islamic Cooperation (OIC) adopted the competing Cairo Declaration on Human Rights in Islam (CDHRI), with arguably "a shared interest in disarming international criticism of their domestic human rights record" (quote from Brems, 2001, on Wikipedia), a document which has been condemned by some because it arguably undermines the rights to equality and freedom of expression and religion, inter alia, set forth in the UDHR and related covenants, "to the point that certain essential provisions are below the legal standards in effect in a number of Muslim countries" (quote from ICJ on Wikipedia).
In 2000, the Nineteenth Session of the Islamic Conference of Foreign Ministers (of the OIC), "recognizing the obligations and endeavors of the Member States to promote and protect the internationally recognized human rights while taking into account the significance of their religious, national and regional particularities and various historical and cultural backgrounds, and with due regard to the “Cairo Declaration on Human Rights in Islam”" adopted the Resolution 60/27-P whereby section 1 states that it:
Welcomes the unanimous decision of the Nineteenth Session of the Islamic Conference of Foreign Ministers to issue the Cairo Declaration on Human Rights in Islam as a general guideline for Member States in the field of human rights.
And therefore this CDRHI instrument has become the "guideline" for the 57 current member states of the OIC1. Then in 2004 the Arab Charter on Human Rights was adopted by the League of Arab States, and was first ratified by Saudi Arabia; some of its provisions have been deemed incompatible with international norms and standards by the then High Commissioner for Human Rights, Louise Arbour. It contains the following in its preamble:
[...] reaffirming the principles of the Charter of the United Nations, the Universal Declaration of Human Rights and the provisions of the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights, and having regard to the Cairo Declaration on Human Rights in Islam
The States parties to the Charter have agreed as follows:
Some International non-governmental organizations have concluded that:
The vast majority of the Member States of the OIC are signatories to the UDHR and the International Covenants, the ICCPR and ICESCR. By adopting the 1990 Cairo Declaration those States are in effect reneging on the obligations they freely entered into in signing the UDHR and the two covenants.
- Does this "in effect reneging" constitute formal non-compliance under public international law; is it required to fully internalize (the Cairo Declaration/Arab Charter on Human Rights) rules to be in non-compliance with a state's obligations arising under these international legal instruments, or does the stated intent (to arguably lower the bar for some rights and freedoms by reference to Sharia law constructs, or through enabling capital punishment, for instance) suffice; does the signing of the Arab Charter on Human Rights change anything, does its preamble weaken or strengthen the support for the Cairo Declaration, does that Arab Charter afford better protection for human rights than Cairo does?
- Incidentally, can it be said there has been a trend in the last 20 years for many states to make rules (internally) or instruments between them (externally, outside the U.N.'s framework, for instance bilateral, multilateral) which formally or in effect renege on the state's obligations under the UDHR and the two related covenants?
- Irrespective of the possible qualifying of the UDHR as customary international law, is the case of compliance by Saudi Arabia different because it never showed any approval for nor has signed the human rights foundational instruments of the United Nations discussed below, even though it has ratified an instrument which reaffirms their principles in its preamble later on; does the U.N. Charter include and make binding by reference the foundational instruments' rules insofar as they provide the substantive content for the Charter's generic freedoms and rights?
1 This is a very cursory overview of a specific string of events and international legal instruments and I'm no expert in the field, hence the question. It should be noted that the (non-)participation to the signing of the foundational instruments or the reliance on the Cairo Declaration or other as a "guideline" has not impeded specific initiatives by such and such a country in the field of human rights, which should always be commended. Nor should the signing or formal support for any instrument be construed as a guarantee of compliance in effect in such and such a case, maybe even less so today with the rise of and the enabling of the far right by some, and with some historical leaders, including from the Security Council of the U.N., utterly failing imho to protect and who sometimes even undermine the very human rights they promised to fight for and which constitute the underpinnings of the U.N. Charter.