It is unlawful and a violation of this chapter for: any person eighteen years or older to forcibly take away a child from, or wrongfully encourage him to leave, the legal or physical custody of any person, agency, or institution in which the child lawfully resides or has been legally placed for the purpose of care, support, education, or adoption, or any person who knowingly detains or harbors a child whom he has reasonable grounds to believe has escaped or fled from the custody of any agency or institution in which the child lawfully resides or has run away from his parent, guardian, or custodian. (Ord. 11-22-88C § 1(C))