in·ter·ven·tion·ist 
(ĭn′tər-vĕnshə-nĭst)
(ĭn′tər-vĕnshə-nĭst)adj.
Relating to or advocating interventionism.
n.
1. One who favors or advocates interventionism.
2. One who organizes or leads interventions, as in confronting a person's substance abuse.