A person is guilty of unlawful assembly if:
1. He assembles with 5 or more other persons with intent to engage in conduct constituting a riot; or being present at an assembly that either has or develops a purpose to engage in conduct constituting a riot, he remains there with intent to advance that purpose; and
2. He knowingly fails to comply with an order to disperse given by a law enforcement officer to the assembly.
3. Unlawful assembly is a Class E crime.