§ 104 Neglect of officer respecting unlawful assembly a misdemeanor.

Here's what this rule means:

If a police officer or magistrate finds out about an unlawful or riotous gathering, they have a duty to act. They must go to the scene, or get as close as they safely can, and use their authority to break up the crowd and arrest the people responsible. This rule makes clear that officers can't ignore the situation once they know about it.

If an officer or magistrate learns about this kind of gathering and simply fails to respond, they have committed a crime themselves. Specifically, they can be charged with a misdemeanor for neglecting their duty. The law treats this kind of inaction seriously because public officials are expected to step in and stop dangerous or unlawful crowds from causing harm.

In short, this rule holds officers accountable. It's not enough for them to know about a riot or unlawful gathering. They are legally required to respond and take action to stop it and arrest those involved. If they don't, they can face criminal charges for that failure.