The Banjar is the smallest formal social entity of Balinese society. It stands above the police and watches over the cultural values of society. The Banjar is also considered by many as a kind of Mafia, as they collect money of residents for all sorts of events. These are often declared as "donations", but unlike donations, you do not have a choice whether or how much you want to pay, because the amounts and frequency are prescribed by the Banjar. You might have heard rumours already about student parties in villas where they had to pay money to the Banjar to get approval. The general rule is, if there are less than 20 people and the music is not too loud, there should not be a problem. However, if you make a pool party with over 50 people, you should contact the responsible Banjar and ask for permission. They will usually also put security to make sure nothing will happen to anyone.
You can recognize the Banjar from their black and white sarongs.
The Banjar maintains a building, a meeting place where community meetings and other activities (sports, dance, Gamelan etc.) take place. Each Banjar is headed by a 'Klian' elected by the General Assembly of the Family Heads. The Banjar is a very old establishment in Bali, which probably dates back to prehistoric times. The villages in Bali consist mostly of several banjars, because a new one is founded when a maximum of 500 inhabitants is exceeded.