Illegal is the opposite of Citizen. Civilian is a type of Citizen. 
Mouth can be used for Drinking. you are likely to find Bridge in/at/on Mouth. you are likely to find Stream in/at/on Bridge. 
Illegal <--Antonym--> Citizen <--IsA-- Civilian 
Drinking <--UsedFor-- Mouth <--AtLocation-- Bridge <--AtLocation-- Stream 