Section 30. Whoever wilfully causes, or aids and abets in causing, wages for personal services exempt from attachment to be attached by trustee process in order to unlawfully hinder or delay their payment to the person to whom they belong shall, on complaint of the person injured thereby or of the guardian or other person having the lawful custody of any such person incompetent to act, be punished by a fine of not more than fifty dollars, to the use of the person injured thereby.