This Practice Note examines the Employment Relations Act 1999 (Blacklists) Regulations 2010, which generally prohibit the compilation, use, sale or supply of blacklists containing details of trade union members and activists whose purpose is to discriminate against workers on grounds of trade union membership or trade union activities. The Practice Note considers the meaning of a prohibited list, protections offered to workers on a blacklist, exceptions to the general prohibition, refusal of employment or employment agency services, detriment and dismissal, time limits, remedies, breach of statutory duty and burden of proof.