war_for_imprison_effect

war_for_imprison_effect = {
	$LIEGE$ = { save_temporary_scope_as = liege_temp }
	$REBEL$ = {
		save_temporary_scope_as = rebel_temp
		save_scope_value_as = {
			name = war_for_imprisonment_flavour
			value = yes
		}
		start_war = {
			casus_belli = refused_liege_demand_war
			target = scope:liege_temp
		}
	}
	# Disgruntled vassals
	if = {
		limit = {
			scope:liege_temp = { NOT = { has_imprisonment_reason = scope:rebel_temp } }
		}
		scope:liege_temp = {
			every_vassal = { #Vassals joining the rebel.
				limit = {
					vassal_would_join_rebel_faction_base_trigger = yes
					OR = {
						#Lovers and friends always back rebel (unless also lovers/friends of the liege)
						vassal_would_join_rebel_faction_relation_trigger = yes
						#Vassals that either like recipient or have high honor will rally if the liege is being tyrannical.
						AND = {
							# Special imprisonment checks
							NOT = {
								scope:liege_temp = { has_imprisonment_reason = scope:rebel_temp }
							}
							# If they can't join a faction against the liege they should not revolt
							vassal_would_join_rebel_faction_tyranny_trigger = yes
						}
						#And finally, vassals that really hate their liege will join regardless (provided that they also do not hate recipient).
						AND = {
							OR = {
								opinion = {
									target = scope:rebel_temp
									value >= -25
								}
								AND = {
									has_game_rule = hard_difficulty
									scope:liege_temp = { is_ai = no }
									opinion = {
										target = scope:rebel_temp
										value >= -50
									}
								}
								AND = {
									has_game_rule = very_hard_difficulty
									scope:liege_temp = { is_ai = no }
									opinion = {
										target = scope:rebel_temp
										value >= -75
									}
								}
							}
							OR = {
								opinion = {
									target = scope:liege_temp
									value <= -40
								}
								AND = {
									has_game_rule = hard_difficulty
									scope:liege_temp = { is_ai = no }
									opinion = {
										target = scope:liege_temp
										value <= -20
									}
								}
								AND = {
									has_game_rule = very_hard_difficulty
									scope:liege_temp = { is_ai = no }
									opinion = {
										target = scope:liege_temp
										value <= 0
									}
								}
							}
						}
					}
					# TGP bloc members follow their leader
					trigger_if = {
						limit = { exists = house.house_confederation.leading_house.house_head }
						house.house_confederation.leading_house.house_head = this
					}
				}
				add_to_list = joining_vassals
			}
		}
	}
	# Bloc members join despite legality
	bloc_member_join_war_effect = yes
	every_in_list = {
		list = joining_vassals
		vassal_join_rebel_war_effect = yes
	}
	every_player = {
		limit = { is_vassal_of = scope:liege_temp }
		scope:liege_temp = {
			save_scope_as = actor
			save_scope_as = puppet_or_actor
		}
		scope:rebel_temp = { save_scope_as = recipient }
		trigger_event = char_interaction.0232
	}
	scope:rebel_temp = {
		add_opinion = {
			target = scope:liege_temp
			modifier = attempted_arrest_opinion
		}
	}
}

As written in game/common/scripted_effects/00_interaction_effects.txt.