Press summary (PDF)
The Hodkin case concerned an apparently straightforward question of statutory interpretation. Were premises
used as a "church" by the Church of Scientology a "place of meeting for religious worship" within the meaning of the Places of Worship Registration Act 1855 section 2 (PWRA). The Court of Appeal in the Segerdal case had answered the same question, in relation to different premises, with a NO. The Supreme Court overruled the Segerdal case with the result that the premises in question must now be registered under PWRA section 2 and it becomes possible for Louisa Hodkin and her fiancee to be married there.
Overview of the judgment:
One might have expected that the case would have been decided on "human rights" grounds by applying Article 9 of the European Convention on Human Rights. The appellants put forward arguments based on the convention. However, the Supreme Court was able to decide the case by interpretation, in the light of present day circumstances, of the words "religious worship."
Note that the Supreme Court accepted as accurate a statutory declaration from the Church of Scientology Minister. The declaration covered the history, beliefs and practices of Scientology. The Minister's evidence was not challenged. Lord Toulson considered the Minister's evidence at paras. 15 to 22. Next, Lord Toulson looked at the Segerdal decision - para. 23 - 30.
Lord Toulson continued (at 31) by saying that whether services performed in the chapel are properly to be regarded as a form of religious worship is inevitably conditioned by whether Scientology is to be regarded as a religion. At  Lord Toulson said that the expression "a place of meeting for religious worship" has to be interpreted in accordance with contemporary understanding of religion and not by reference to the culture of 1855 (when, of course, Scientology did not exist).
Interestingly from the viewpoint of the law of precedent, Lord Toulson then referred to an American case Malnak v Yogi 592 F.2d 197 (1979) and a High Court of Australia case - Church of the New Faith v Commissioner of Payroll Tax (Victoria) (1983) 154 CLR. Such decisions cannot bind English courts but may have persuasive force.
Lord Toulson  said that unless there is some compelling contextual reason for holding otherwise, religion should not be confined to religions which recognise a supreme deity. "Ideas about the nature of God are the stuff of theological debate" . For the purposes of the Charities Act 2011, the word "religion" was not confined to religions that believe in a God . Here was an indication (in an Act of Parliament) that the understanding of religion in today's society is broad . Furthermore, PWRA section 2 showed, by the language used, an intentionally broad sweep extending to "any other body or denomination of persons" .
At , Lord Toulson said:
"For the purposes of PWRA, I would describe religion in summary as a spiritual or non-secular belief system, held by a group of adherents, which claims to explain mankind’s place in the universe and relationship with the infinite, and to teach its adherents how they are to live their lives in conformity with the spiritual understanding associated with the belief system. By spiritual or non-secular I mean a belief system which goes beyond that which can be perceived by the senses or ascertained by the application of science. I prefer not to use the word “supernatural” to express this element, because it is a loaded word which can carry a variety of connotations. Such a belief system may or may not involve belief in a supreme being, but it does involve a belief that there is more to be understood about mankind’s nature and relationship to the universe than can be gained from the senses or from science. I emphasise that this is intended to be a description and not a definitive formula."
At  Lord Toulson said that, on the approach he had taken to the meaning of religion, the evidence was amply sufficient to show that Scientology was within it. The meaning given to worship in Segerdal was unduly narrow, but even if it was not unduly narrow in 1970, it is unduly narrow now .
The expression "religious worship" was wide enough to include religious services, whether or not the form of service falls within the narrower definition in Segerdal. This view was supported by dictionary definitions of "worship" . The authorisation of premises should not depend on "fine theological or liturgical niceties" which were "more fitting for theologians than for the Registrar General or the courts .
Brief note on the European Convention:
From a European Convention on Human Rights perspective it is worth noting that Article 9 refers to freedom of thought, conscience and religion. The State may not impose restrictions on that. However, the State may, in specified situations (Art 9.2) impose restrictions on the "manifestation" of religion or belief. Under the Convention, "religion" has been held to cover not only the major world religions. For example, Rastafarianism was accepted in R v Taylor  EWCA Civ 2263. There is no need, for convention purposes, to enter into abstract discussion about the nature of religion since what is not a religion may well be a "belief" and, as such, still entitled to protection under the convention. See R (Williamson) v Secretary of State for Education and Employment  UKHL 15.
Manifestation of religion has resulted in a considerable body of case law - e.g. R (Begum) v Governors of Denbigh High School  UKHL 15.
Addendum 13th December:
Church versus State: Scientology faces unholy war after court ruling