While doing some more research and testing I discovered some interesting fact. If I change the order of the tables in my view definition the trigger works.

So instead of

from 

(select fnc.id fnc_id,fnc.name fnc_name,lst.* 

from us_functions fnc, us_lists lst 

where lst.list_type = 1) lst

left join us_list_values liv

on liv.lst_id = lst.id and liv.fnc_id = lst.fnc_id

 

It needs to be

from 

us_list_values liv 

Right join (select fnc.id fnc_id,fnc.name fnc_name,lst.* 

from us_functions fnc, us_lists lst 

where lst.list_type = 1) lst

on liv.lst_id = lst.id and liv.fnc_id = lst.fnc_id 

Can anyone explain why this makes a difference ?