Cal. Pen. Code § 290.002
Persons required to register in their state of residence who are out-of-state residents employed, or carrying on a vocation in California on a full-time or part-time basis, with or without compensation, for more than 14 days, or for an aggregate period exceeding 30 days in a calendar year, shall register in accordance with the Act. Persons described in the Act who are out-of-state residents enrolled in any educational institution in California, as defined in Section 22129 of the Education Code, on a full-time or part-time basis, shall register in accordance with the Act. The place where the out-of-state resident is located, for purposes of registration, shall be the place where the person is employed, carrying on a vocation, or attending school. The out-of-state resident subject to this section shall, in addition to the information required pursuant to Section 290.015, provide the registering authority with the name of his or her place of employment or the name of the school attended in California, and his or her address or location in his or her state of residence. The registration requirement for persons subject to this section shall become operative on November 25, 2000. The terms "employed or carries on a vocation" include employment whether or not financially compensated, volunteered, or performed for government or educational benefit.
Ca. Pen. Code § 290.002