Except in so far as in any particular case any privilege or immunity is waived by the Secretary General of the United Nations, persons employed on missions on behalf of the United Nations shall enjoy—
(a) While exercising their functions as such, as during their journey to and from the places of meeting, immunity from personal arrest or detention and from seizure of their personal baggage and inviolability for all papers and documents:
(b) Immunity from legal process of every kind in respect of words spoken or written and all acts done by them in the exercise of these functions.