The Ireland/Northern Ireland Protocol was at the heart of the Withdrawal Agreement negotiated with the EU in 2019 and was, as required by that agreement, incorporated into UK law. It has important tax implications, especially in the areas of VAT, customs duties and state aid. The Northern Ireland Protocol Bill would remove most of the Protocol from UK law, despite the UK’s treaty obligation. The government claims that the principle of ‘necessity’ gives a legal basis for that action in international law, but its argument is unconvincing. The Bill is likely to run into considerable opposition in Parliament, especially in the House of Lords. And if passed it would threaten a trade war with the EU with major implications.