A duly authorized security guard may detain within the terminal any person committing an act declared unlawful by any provision of sections 577.700 to 577.718 and section 307.176^* until law enforcement authorities arrive. Such detention shall not constitute unlawful imprisonment and neither the company nor such company representative personally shall be civilly or criminally liable upon grounds of unlawful imprisonment or assault providing that only reasonable force is exercised against any person so detained.