United Kingdom

23andMe, AncestryDNA and MyHeritage do not allow law enforcement use of their databases without a warrant. FamilyTreeDNA offers an ‘opt-out from law enforcement matching’ possibility, and all European users are automatically opted out in line with the EU General Data Protection Regulation (GDPR). Contributors to GEDmatch, which allows law enforcement use of ‘public’ profiles with permission in serious cases, must actively opt in to law enforcement matching.

https://www.gov.uk/government/publications/use-of-genetic-genealogy-techniques-to-assist-with-solving-crimes/should-we-be-making-use-of-genetic-genealogy-to-assist-in-solving-crime-a-report-on-the-feasibility-of-such-methods-in-the-uk-accessible-version

Familial searching has been used in the UK for serious crimes since 2003. The technique uses standard STR-based DNA profiles and ranks the likelihood of a familial relationship between an unknown individual who has left DNA at a crime scene and individuals on the National DNA Database. This technique can only identify parents, children or siblings and the success rate is around 20%.