(da war es vor ein paar wochen, jetzt jedoch leider nicht mehr. dennoch, hier der eintrag - hab ich mir damals rauskopiert, weil ich das selbst brauchte:)
Use of -ise and -ize
Words of the sort organize/organise and their derivatives can be spelt with either s or z. The -ize forms are promoted by the Oxford English Dictionary and are the forms used by most publications issued by the Oxford University Press and in much other academic publishing. This is sometimes known as OED spelling and may be marked by the registered IANA language tag en-GB-oed. It is the spelling used by the Encyclopædia Britannica, by the United Nations (mostly), and by the majority of international standards groups. The -ize forms are also given priority in all dictionaries issued by Oxford, Cassell, Collins, Longman, and Penguin, and also in dictionaries issued by Chambers for international use. These forms were used by The Times until the mid-1980s. The -ise forms are now generally used by the British government, within the European Union, by Cambridge University publications, by the media and is taught in the British school system. The -ise forms are preferred in dictionaries from Reader's Digest (UK) and by Chambers in their native-speaker dictionaries and are used by most British publishers and in most British newspapers. Pam Peters (2004, -ize/-ise ) relates that British National Corpus data indicates the ratio of popularity for -ise forms to -ize forms in Britain is 3:2. The -ize forms were introduced by Noah Webster in the USA in his American Spelling Book and subsequent dictionary, on the grounds that they more correctly reflected the original Greek etymology of the -ize suffix.