European Convention for the Protection of Animals for Slaughter

The European Convention for the Protection of Animals for Slaughter, also known as the Slaughter Convention, is an animal welfare treaty of the Council of Europe, adopted on 10 May 1979 in Strasbourg, and effective since 11 June 1982. It establishes ethical standards pertaining to animal slaughter, such as stunning.
Development.
Due to increased public awareness and debate about animal welfare in the 1960s, the Council of Europe became more concerned with the topic, and adopted a convention of minimum requirements for animal transport in 1968. Next, it adopted the European Convention for the Protection of Animals kept for Farming Purposes (or Farm Animal Convention) in 1976. The European Convention for the Protection of Animals for Slaughter (or simply Slaughter Convention) followed in 1979, and was revised in 1991. All these conventions were based on animal welfare recommendations resulting from the latest scientific research in applied ethology. The Farm Animal Convention worked as an overarching, open framework law that could be further elaborated later, while the transport and slaughter conventions were much more detailed, 'closed' and finalised in character.
Contents.
The stated purpose of the Slaughter Convention is 'to help harmonise methods of slaughter in Europe and make them more humane.' The first set of provisions sets standards for the treatment of animals in slaughterhouses: 
The second set of provisions regulates the killing process itself, stating that 'slaughter must be effected in such a way as to spare the animals any unnecessary suffering'. 
Status.
The Slaughter Convention forms part of the core of European legislation concerning animal welfare, which also includes the European Convention for the Protection of Animals kept for Farming Purposes (1976, with its 1992 Protocol of Amendment), the European Convention for the Protection of Animals during International Transport (revised in 2003, replaced the 1968 original), the European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (1986, with its 1998 Protocol of Amendment; see also Directive 2010/63/EU), and the European Convention for the Protection of Pet Animals (1987).
As of May 2021, 26 states have ratified or succeeded/acceded to the Slaughter Convention, and four states have only signed it; neither the European Union nor the other states have yet done so.