NZ has had a quasi-monopoly on low-quality lamb and mutton in the EU since this was negotiated as part of the UK entry package in 1973. The British Isles (that includes the Irish Republic) were pretty much set up as the main higher-quality producers to the EEC (to the immediate detriment of producers elsewhere, France for example). That situation has since settled down somewhat, since there are in fact national and regional tastes to be considered, (comparative advantage doesn't appear to take that into account), such as British lamb being fatter than French taste enjoys, or there being a market for very young lamb in Spain. So national and regional production has gradually built up again.