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Under the UK’s post-Brexit settlement with the EU, Northern Ireland remains part of the UK’s customs territory, but has to apply EU customs and other goods-related laws. This arrangement, now referred to as the Windsor Framework, means there is no ‘hard’ border on the island of Ireland and no customs or regulatory controls on goods moving between Northern Ireland and the Republic of Ireland, which is part of the EU’s customs territory.
If the US targets EU goods for further tariffs while sparing the UK, differences in the tariff rates applied to EU and UK goods may have important implications for Northern Ireland.