Sch 3 para 20
Import and export controls and trade with any place outside the United Kingdom but not— (a) the furtherance of the trade of Northern Ireland or the protection of traders in Northern Ireland against fraud; (b) services in connection with, or the regulation of, the quality, insurance, transport, marketing or identification of agricultural or food products, including livestock; (c) the prevention of disease or the control of weeds and pests; (d) aerodromes and harbours; (e) any matter within paragraph 4 of Schedule 2.