When the commissioner shall find that any person has violated any of the provisions of this article, he or his duly authorized agent or agents may institute proceedings in a court of competent jurisdiction: Provided, however, That no prosecution under this article shall be instituted without the defendant first having been given an opportunity to appear before the commissioner or his duly authorized agent to introduce evidence, either in person or by agent or attorney, at a hearing. If, after such hearing, or without such hearing in case the defendant or his agent or attorney fails or refuses to appear, the commissioner is of the opinion that the evidence warrants prosecution, he shall proceed according to law.