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Religious freedom and customary international law


The struggle for religious freedom is the oldest of all movements for international human rights. Nonetheless, religious freedom remains the most problematic of all human rights. Despite treaty protections for religious rights stretching from the Treaty of Westphalia (1648) to the European Convention on Human Rights (1950) and beyond, the role of customary international law remains considerable. For example, how does one define such rights as the freedom to establish religious institutions, the right to practice a religion, and the right to preach and spread a religion? The definition and enforcement of these and other religious rights all depend on customary international law. Indeed, customary international law is vital in protecting religious liberties, threatened world-wide by hostile state practices.

What is customary international law? There are about as many theories about the nature of customary international law as there are international lawyers. I elaborate my approach to customary international law in my treatise, International Law, 7th Edition (2016), Wolters Kluwer. I believe that customary international law is more an art than a science. (p. 46) Customary international law is determined on the basis of an historical record of consistent state practice and a psychological element sometimes termed opinio juris. “Opinio juris may be thought of as a solvent that transforms the nitty-gritty of a historical rendition of examples of state practice into a more liquid form: a rule of customary international law that may be applied to current problems.” (p. 48) So far, my approach is reasonably common amongst international lawyers. However, I go a little further and suggest that “jurists and judges, rather than states, are often more helpful sources for expressions of opinions that international practice has at some stage become customary international law.”

Looking more at the opinio juris of jurists and judges than that of states is especially valuable in discerning the customary international law of religious freedom. For thousands of years, the religious liberties of minority religions have been violated by states, who often despite their treaty commitments, actively enforce the preferences of their majoritarian religions. State practice may in do more to contradict a rule of religious toleration than to promote it. Indeed, an alliance between the power of the state and the majoritarian religion has been more common than not, each buttressing the other. Typically, minority religions are viewed as threats both to the unity of the state and to the dominance of the majoritarian religion. This is a common thread from antiquity to the present day. Even the European Court of Human Rights, usually a staunch protector of many other international human rights, gives unusual and undue weight to the protection of the religious sensibilities of a state’s majoritarian religion, rather than to protecting minority faiths. This turns the European Convention on Human Rights, ordinarily employed to shelter the strong against the weak, on its head.

Europe traditionally has been hostile to religious freedom. From the Roman Empire to the present day, the Continent has witnessed one after another bloody religious struggle. Rome at first violently suppressed Christianity. Christianity, once established as the state religion dissolved into 1700 years of doctrinal and physical clashes, including the 11th century schism between the Rome and the Catholic West and Constantinople and the Orthodox East. There were the horrific wars in the 16th and 17h centuries between Rome and the dissenting Protestants.  In the 20th century, religious bigotry contributed to the slaughter of millions of European Jews. Today anti-Semitism remains a threat alongside widespread European intolerance of Islam. Elsewhere, there are anti-Christian ideologies and practices in many Islamic nations. Majoritarian religious cultures are too often intolerant of religious diversity in Europe and elsewhere.

Remarkably, it took 43 years from the conclusion of the European Convention on Human Rights and Fundamental Freedoms for the European Court of Human Rights to find a state in violation of the Convention’s Article 9. Article 9 provides, inter alia, that “Everyone has the right to freedom to freedom of thought, conscience and religion; this right includes freedom to change his religion or belief and freedom, either alone or in community with others and in public or private, to manifest his religion or belief, in worship, teaching, practice, and observance.” The landmark case from the Strasbourg Court was Kokkinakis (25 May 1993), where the right of Mr. Kokkinakis to manifest his religion as a Jehovah’s Witness by preaching to the public was upheld against Greece. The Court held that individuals had the “right to try to convince one’s neighbors” to abandon the majoritarian religion for a small dissenting faith.

Sadly, Kokkinakis has not been much followed in the Court’s practice. Instead, Strasbourg has used Article 9 to protect the sensibilities of the majoritarian religion against minority views or denominations. So, for example, in Otto-Preminger (20 September 1994) the Court upheld Austrian suppression of a movie that mocked the Roman Catholic religion. In doing so, it stressed that the “Court cannot disregard the fact that the Roman Catholic religion is the religion of the overwhelming majority of Tyrolians.” More of the same followed in Murphy (10 July 2003) where the Court permitted Ireland to prohibit a Protestant radio broadcast in that Roman Catholic state because that prohibition was “prudent”. And in Lautsi (18 March 2011) the Court overturned the decision of a chamber when it upheld the right of Italy to require the display of a crucifix in public classrooms, rejecting the application of non-believing parents on the grounds that there was “no evidence’ that such a display could “have an effect on young persons”.

Examples could be multiplied across Europe and, more broadly, across the globe. In short, majoritarian religions are often supported by the state, and in turn support the state. The role of formal international law and international courts in protecting minority persuasions has been and remains limited. It is only in the opinions of jurists in constituting opinio juris in customary international law, where international law comes out strongly for religious freedoms. Whether or not this alone can make up any form of customary international law depends greatly on the theoretical approach to customary international law held by any of us.


Mark Weston Janis is the William F Starr Professor of Law at the University of Connecticut, and a Visiting Fellow and formerly Reader in Law at the University of Oxford.


Cite as: Mark Weston Janis, “Religious Freedom and Customary International Law”, Völkerrechtsblog, 8 March 2019, doi: 12345678.

Mark Weston Janis 
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  1. Hello, are there any scholars that have shared their views of the Customary law practice for thought, conscience and religion?
    Ricky Frost

  2. Thank you for this great introductory piece regarding a very interesting topic.

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