Cal. Rev. & Tax. Code § 25122

For purposes of allocation and apportionment of income under this act, a taxpayer is taxable in another state if (a)in that state it is subject to a net income tax, a franchise tax measured by net income, a franchise tax for the privilege of doing business, or a corporate stock tax, or (b)that state has jurisdiction to subject the taxpayer to a net income tax regardless of whether, in fact, the state does or does not.