Mercury sable passenger side mirror

I most states a car has to have all it's original equipment in good operating condition to pass inspection. That mirror was there for a reason and it would be a good idea to replace it. Maybe a salvage yard could help you find one for less.

I would worry less about whether it's legal and more about whether it's safe. Get one from a Pull A Part, they're cheap. Sable and Taurus are basically the same thing.