Labor Code § 4150
CHAPTER 8. Election to Be Subject to Compensation Liability
When an employer has in his employment any person not included within the term “employee” as defined by Article 2 of Chapter 2 of Part 1 of this division or a person not entitled to compensation under this division, such employer and such person employed by him may, by their joint election, come under the compensation provisions of this division in the manner hereinafter provided.