A more thorough explanation:

A ban is a public proclamation or summons that can deal with a variety of matters. It can be used to call a lord's vassals to arms or to proclaim that an offender is now considered an outlaw. In ecclesiastical law, a ban is an authoritative prohibition, such as an interdict or excommunication. It can also refer to the banns of matrimony. To ban something means to prohibit it, especially by legal means.

• A king might issue a ban to call his knights to battle.
• The church might issue a ban to excommunicate someone who has committed a serious sin.
• Before a wedding, the banns of matrimony are read aloud in church to announce the upcoming marriage.
• The government might ban the use of certain drugs or weapons.

These examples illustrate how a ban can be used in different contexts, from military to religious to legal. A ban can be used to summon people to action or to prohibit certain behaviors or actions. It is a powerful tool that can have significant consequences for those affected by it.