Cal. Code Regs. tit. 18 § 24349(c)
If an intangible asset is known from experience or other factors to be of use in the business for only a limited period, the length of which can be estimated with reasonable accuracy, such an intangible asset may be the subject of a depreciation allowance. Examples are patents and copyrights. An intangible asset, the useful life of which is not limited, is not subject to the allowance for depreciation. No allowance will be permitted merely because, in the unsupported opinion of the taxpayer, the intangible asset has a limited useful life. No deduction for depreciation is allowable with respect to goodwill.
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** Except for the deletion of the last sentence of the federal regulation, this regulation is the same as section 26 CFR 1.167(a)(3).
Cal. Code Regs. Tit. 18, § 24349(c)