Permits to work and to employ and certificates of age shall always be open to inspection by supervisors of attendance, probation officers, designees of the Labor Commissioner, and by officers of the Superintendent of Public Instruction. Every permit to work or to employ and every certificate of age shall be subject to cancellation at any time by the Superintendent of Public Instruction, the Labor Commissioner, or by the person issuing the permit or certificate whenever any person authorized to inspect such permits and certificates finds that the conditions for the legal issuance of the permit or certificate of age do not exist or did not exist at the time the permit or certificate was issued. A permit to work shall be revoked by the issuing authority when he is satisfied that the employment of the minor is impairing the health or education of the minor, or that any provision or condition of the permit is being violated, or that the minor is performing work in violation of any provision of law.