No but PA is their butt buddy about it (as is NJ and NYC with their intrudcion of aftermarket parts needing CARB-EO numbers like Cali started mid-2014). My Mustang hasn't had a legal inspection on it since 2009 it would pass safety inspection but emissions is out the door.
Early OBDII can be tricked (i.e. these little things called MIL eliminators that plug into your rear o2 sensors to trick the ECM into thinking the car still has its converters), and around 04 when things started advancing, it made it a bit easier to just re-tune the vehicle... makes it run without certain emissions stuff, and actually improves fuel economy and horsepower as long as the person writing the tunes knows what they're doing.
The front non-heated o2's are needed to tell the ECM what the air/fuel ratio is and adjust it accordingly. The rear heated ones are there to make sure the catalatyc converters are getting hot enough that they will burn off any unburnt fuel. If you get rid of restrictions like stock exhaust manifolds for headers, cold air intake, better flowing mufflers, etc as well as a tune, that unburnt fuel issue isn't much of an issue anymore.
With how much improvement engines have made over the past 10-15 years, I can see the things that were added back in the 80's and 90's to be eliminated. But the EPA wants their money.