No person under the age of 18 years shall have in his or her possession, care, custody or control any of the articles mentioned in § 9.50.010 except within his or her own domicile or except when accompanied by and under the immediate supervision of a parent or guardian or having in his or her possession written permission signed by such parent or guardian permitting him or her to have any of the articles in his or her possession.
(`78 Code, § 9.50.020.)