The term is widely used to refer to more esoteric entities in a number of disciplines, including
- philosophy, when a concept is not available;[clarification needed]
- biology, when a species does not fit into a genus which includes other species;
- law, when a special and unique interpretation of a case or authority is found to be necessary;
- intellectual property rights, where there is no defining characteristic;[clarification needed] and
- politics and societal norms, where there is no real authority perceived.[clarification needed]
In the taxonomical structure "genus → species", a species is described as sui generis if its genus was created to classify it (i.e., its uniqueness at the time of classification merited the creation of a new genus, the sole member of which was initially the sui generis species). A species that is the sole extant member of its genus (e.g. the Homo genus) is not necessarily sui generis: extinction may have eliminated other species of that genus.
In law, it is a term of art used to identify a legal classification that exists independently of other categorizations because of its singularity or due to the specific creation of an entitlement or obligation. For example, a court's contempt powers arise sui generis and not from statute or rule. The New York Court of Appeals has used the term in describing cooperative apartment corporations, mostly because this form of housing is considered real property for some purposes and personal property for other purposes.
When citing cases and other authorities, lawyers and judges may refer to "a sui generis case", or "a sui generis authority", meaning it is a special one confined to its own facts, and therefore may not be of broader application.
In statutory interpretation, it refers to the problem of giving meaning to groups of words where one of the words is ambiguous or inherently unclear. For example, in criminal law, a statute might require a mens rea element of "unlawful and malicious" intent. Whereas the word "malicious" is well-understood, the word "unlawful" in this context is less clear. Hence, it must be given a meaning of the same kind as the word of established meaning.
Two or more words are connected by "and", as opposed to "or" are particularly susceptible to vagueness. The interpretation of the two or more words might therefore have a sui generis difference depending on the circumstances. Courts sometimes have to attribute a conjunctive (X 'and' Y) intention to the legislature even though the list is disjunctive (X 'or' Y) because, otherwise, no overall interpretation of the law in question would make sense.
In British town planning law, such as the Town and Country Planning (Use Classes) Order 1987, many common types of land use are classified in "use classes". Change of use of land within a use class does not require planning permission; however, changing between use classes might require planning permission, but not if the use class is sui generis.
Examples of sui generis transference include embassies, theatres, amusement arcades, laundrettes, taxi or vehicle hire businesses, petrol filling stations, scrapyards, nightclubs, motor car showrooms, retail warehouses, clubs and hostels.
Even qualified and experienced town planners misconceive that changing use from an existing use class to one which is sui generis always requires planning permission; it does not because the property is not transferred between two existing use classes. Permission is only required if the sui generis use is materially different from the existing one, such as from a petrol station where petrol tanks might have leaked. As in other applications of the phrase sui generis, the decisions will be a unique matter of fact, degree, and professional opinion.
Aboriginal law and education
The motto "Sui Generis" has been adopted by the Akitsiraq Law School because it is a sui generis (aboriginal) title in all of Canadian aboriginal law institutes by dint of its title being Inuktitut, the Aboriginal language of the Inuit in the far north of Canada. More importantly, in aboriginal professional legal education, the work of Aboriginal people to define and create contemporary aboriginal education is a thing of its own kind having sui generis admissions and sui generis curriculum.
Intellectual property law
Generally speaking, protection for intellectual property extends to intellectual creations in order to incentivize innovation, and depends upon the nature of the work and its "characteristics". The main types of intellectual property law are: copyright, which protects creative works; patent, which protects invention; and trademark, which protects branding and other exclusive properties of products and services. Any matter that meets such criteria is protected.
However, sui generis statutes exist in many countries that extend intellectual property protection to matter that does not meet characteristic definitions: integrated circuit layouts, ship hull designs, fashion designs in France, databases, or plant varieties require sui generis statutes because of their unique characteristics. The United States, Japan, and many EU countries protect the topography of semiconductor chips and integrated circuits under sui generis laws, which borrow some aspects from patent or copyright law. In the U.S. this sui generis law is known as the Semiconductor Chip Protection Act of 1984.
Politics and society
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In political philosophy, the unparalleled development of the European Union as compared to other international organizations has led to its designation as a sui generis geopolitical entity. The legal nature of the EU is widely debated because its mixture of intergovernmental and supranational elements cause it to share characteristics with confederal and federal entities.
A similar case which has led to the use of the label sui generis is the unique relationship between France and New Caledonia because the legal status of New Caledonia can aptly be said to lie "somewhere between an overseas collectivity and a sovereign nation"; although other examples of such a status for other disputed or dependent territories may exist, this arrangement is certainly unique within the French Republic.
In local government, a sui generis entity is one which does not fit with the general scheme of local governance of a country. For example in England, the City of London and the Isles of Scilly are the two sui generis localities, as their forms of local government are both (for historical or geographical reasons) very different from those of elsewhere in the country. Therefore the The City of London and the Isles of Scilly are said to be sui generis authorities, pre-dating recent reforms of local government. The Joint Council of Municipalities of Croatia is a sui generis council of municipalities to Croatians because it formed after international agreement and therefore has no similar example in the rest of the country. The legal status of the Holy See has been described as a sui generis entity possessing an international personality.
- "sui generis". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005.
- Dictionary.com "Word of the day" 2001-06-14  accessed 2007-10-14
- See Dunway v. New York,442 U.S. 200 (1979).
- See In re Marriage of Betts, 558 N.E.2d 404, 200 Ill.App.3d 26 (1990).
- See Matter of State Tax Commn. v. Shor, 43 NY2d 151, 400 N.Y.S.2d 805, 371 N.E.2d 523 (1977).
- (Hampton, E. (p. 10–11) in Battiste & Barman (Eds.). First Nations Education in Canada: The Circle Unfolds. UBC Press, 1995)