In the case of the State, “law” also means the law of any state providing for the withholding of personal income tax from wages or salaries of its residents employed by other states; provided, that the law of that state, in the determination of the State Controller, provides for withholding of personal income taxes from wages or salaries of its employees residing in California.
Source:
Section 1170.5, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=1170.5..