The Immigration (Control of Entry through Republic of Ireland) (Amendment) Order 1987
Article 4 of the Immigration (Control of Entry through Republic of Ireland) Order 1972 provides, inter alia, that certain persons who do not have the right of abode and who enter the United Kingdom from the Republic of Ireland after coming from a place outside the common travel area or after leaving the United Kingdom while having a limited leave to enter or remain there which has since expired, are prohibited from taking up employment except where they are nationals of States who are members of the European Community other than Greece, Portugal and Spain.