What is required for an assembly to be deemed unlawful?

An assembly is deemed unlawful when a public officer requests that it disperse. This request often stems from a violation of specific laws governing public gatherings, which may include issues related to safety, order, or legal permitting. The authority of a public officer to issue such a request reflects the government's role in maintaining public order and ensuring the rights of all citizens are respected.

The other options do not encapsulate the definition of an unlawful assembly as effectively. For instance, having a minimum number of participants or providing prior notification may not alone determine the legality of an assembly without additional context regarding compliance with regulations. Similarly, the duration of the assembly, such as lasting longer than one hour, does not inherently define its lawfulness; rather, it depends on the circumstances and how the assembly is conducted in relation to the law. Thus, the correct answer accurately reflects the condition under which an assembly can be declared unlawful by an authority.