In the province line you refer to ROOT which is the character that uses the event. You should refer to province scope somehow, something like this should work:
There is lots of examples in events, just search for spawn_unit.Code:effect = { location = { ROOT = { spawn_unit = { province = PREV troops = { light_cavalry = { 100 100 } light_infantry = { 1000 1000 } heavy_infantry = { 250 250 } knights = { 25 25 } archers = { 500 500 } } } } } scaled_wealth = -0.20 }
Or he could scope to the location of ROOT instead of ROOT the character, I think that also should work.