The Collaborative International Dictionary of English v.0.48:

nonparticipation \nonparticipation\ n.
   withdrawing from the activities of a group.

   Syn: non-engagement, non-involvement.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonparticipation
    n 1: withdrawing from the activities of a group [syn: non-
         engagement, nonparticipation, non-involvement] [ant:
         engagement, involution, involvement, participation]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "nonparticipation":
   a wise passiveness, contemplation, contemplative life,
   do-nothing policy, do-nothingism, do-nothingness, dormancy,
   idleness, immobility, inaction, inactivity, indolence, inertia,
   inertness, laissez-aller, laissez-faire, laissez-faireism,
   meditation, neutralism, neutrality, neutralness, noninvolvement,
   nonresistance, nonviolence, nonviolent resistance, pacifism,
   paralysis, passive resistance, passive self-annihilation,
   passiveness, passivism, passivity, policy, procrastination,
   quiescence, quietism, stagnancy, stagnation, standpattism, stasis,
   vegetation, vita contemplativa, waiting game,
   watching and waiting