If a person employed as a watchman or guard believes that a person is trespassing on posted property that is used for a defense-related activity as defined in § 9-701 of the Criminal Law Article, the employee may detain the person and notify a law enforcement officer. If a law enforcement officer has probable cause to believe that a person has trespassed on posted property that is used for a defense-related activity as defined in § 9-701 of the Criminal Law Article, the law enforcement officer may arrest the person without a warrant for a violation of § 9-702 or § 9-703 of the Criminal Law Article.