Discuss (b) functional necessity of immunities

An international institution (international organization) = an association of states (or of states and other entities) created by treaty, possessing its own organs, will and legal personality, established to pursue common purposes through permanent cooperation. The definition's four notes: treaty-based (the constituent instrument — the UN Charter, the SAARC Charter); institutionalized (organs, staff, headquarters — a continuing machinery, not a conference); voluntary-membered (sovereign equals joining by consent); purpose-driven (the common interest the charter declares).