A marketplace facilitator that is registered with the department or required to register with the department under Chapter 2 (commencing with Section 6051) or Chapter 3 (commencing with Section 6201) and that facilitates a retail sale of tangible personal property by a marketplace seller is the retailer selling or making the sale of the tangible personal property sold through its marketplace for purposes of this part.
Ca. Rev. and Tax. Code § 6043