SQL Create "Admin" right inside SQL Query ( CASE/IF inside WHERE clause)

This is my SQL:

WHERE 
CASE 
    WHEN (UC.USER = SESSION_USER() AND UC.full_access = 1) 
    THEN (FROS.IsVoided = false) 
    ELSE (FROS.IsVoided = false AND UC.USER = SESSION_USER()) 
END

I need that IF user = to (current session user) and full_access = 1 the display X else Y, I can provide more code and tables, but from general view, can someone find any common mistakes which I have done?

As alternatively I have this idea:

WHERE 
IF(UC.USER = SESSION_USER() AND UC.full_access= 1, FROS.IsVoided = false, FROS.IsVoided = false AND UC.USER = SESSION_USER())

WHat is the correct way of using if statement inside WHERE clause?