In countries where the legal system entitles defendants to a jury by their peers, the general public may not be considered sufficiently knowledgeable in a field of practice to act as a peer in some legal cases. For example, the average person may not be able to determine if a civil engineer took reasonable care to ensure a bridge would not collapse. Therefore the government may define self-governing professional associations of peers in specific fields.

As part of their self-governing mandate, professional associations are usually responsible for licensing of practicioners in their field. Furthermore, a person is usually prohibited from advertising as a "professional" unless they are a member in good standing of the relevant professional association.

Medical, engineering, architecture, accounting and legal practitioners are commonly governed by professional associations in most localities.

Examples of professional associations