The Collaborative International Dictionary of English v.0.48:

Nonintervention \Non*in`ter*ven"tion\, n.
   The state or habit of not intervening or interfering; as, the
   nonintervention of one state in the affairs of another.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nonintervention
    n 1: a foreign policy of staying out of other countries'
         disputes [syn: nonintervention, noninterference] [ant:
         interference, intervention]