Scope of regime As part of a general trend towards the stricter control of foreign direct investment, the National Security and Investment Act 2021 (NSIA 2021) came fully into force on 4 January 2022. It establishes a new standalone statutory regime that allows the government to review and intervene in a wide range of investments in businesses (including joint ventures) that are active in the UK or acquisitions of related assets, with the ultimate objective of protecting national security. The ability to ‘call-in’ a transactions under NSIA 2021 applies, retrospectively, to any transaction completed on or after 12 November 2020. The regime falls into two parts: • a mandatory notification regime, which applies from 4 January 2022, such that anyone acquiring control of entities that are active in 17 specific sectors in the UK, will have to be notified to the government and must be cleared before completion. The notification obligation applies regardless of whether: (i) the investor is foreign or UK-based, (ii) the entity is established