What does the Building Code(s) have to say about this?
This house was probably 30+ years old and this wall was opened during a Kitchen renovation. I was told all of the homes in the development were like this.
If an Inspector was here now to inspect some new rough-in items would he, or could he say anything about the trap being over the panel, or that the panel (other side of wall) is now in a Bathroom?
This is an excellent example. I will give you my interpretation, This is not too uncommon and in this installation I think it is permitted. Water can leak down from most anywhere above a panel and if we had to worry about bathrooms/kitchens or any sinks, it would limit us in a lot of dwellings.