These Regulations are made in exercise of the powers conferred by the European Union (Withdrawal) Act 2018 (c. 16) in order to address failures of retained EU law to operate effectively and other deficiencies (in particular section 8(2)(a), (b), (c) and (g) and (9)) arising from the withdrawal of the United Kingdom from the European Union.
Link: The Persistent Organic Pollutants (Amendment) (EU Exit) Regulations 2019
Source: Legislation .gov.uk