The 2019 regulations bring the CLP Regulation (and other chemical legislation) into effect in the whole of the UK: The Chemicals (Health and Safety) and Genetically Modified Organisms (Contained Use) (Amendment etc.) (EU Exit) Regulations 2019, UK SI 2019/720 https://www.legislation.gov.uk/uksi/2019/720/contents/made
The 2020 regulation which take Northern Ireland back out under EC control under the Northern Ireland Protocol: The Chemicals (Health and Safety) and Genetically Modified Organisms (Contained Use) (Amendment etc.) (EU Exit) Regulations 2020, UK SI 2020/1567 https://www.legislation.gov.uk/uksi/2020/1567/contents/made