California Code, Penal Code - PEN § 33315

A permit issued in accordance with this article may be revoked by the issuing authority at any time, when it appears that the need for the short-barreled rifles or short-barreled shotguns has ceased or that the holder of the permit has used the short-barreled rifles or short-barreled shotguns for purposes other than those allowed by the permit or that the holder of the permit has not exercised great care in retaining custody of any weapons possessed under the permit.