Foot massage in some countries is associated with trafficking, this is a good example.
For those interested in the politics, this is a great example, especially because it gives the association strength.
In California, certification is voluntary, meaning it is not required by the state; however, according to CAMTC’s FAQs page, ” … many cities and counties have replaced their requirement for a city massage permit, usually issued by the police or sheriff’s “department, with a requirement for CAMTC certification.”
https://www.massagemag.com/california-massage-therapy-council-fight-trafficking-88804/