Eh, MA already has a law on the books for this. It's called "modified exhaust" and plenty of my friends got tickets for this in our youth.
This law is really geared towards the riders. There are fart cans on everything out here.
Honestly, I am not sure this law has any legal merit to ban aftermarket systems. When was the last time you saw a stock 1986 ford exhaust system for sale? Good luck finding one. You have no choice but to run aftermarket systems.
With the amount of positive comments I get in my mustang from cops...i highly doubt anyone is gonna bother me. And if someone does....well, show me where I can get an oem ford system. I can't.
But like I said...this law is really mostly for the ricers. I can drive around and see stupid fart cans on minivans, or some middle aged woman in her 40's with a fart can on a stock camry. Its out of hand. Cant sleep at night with the window open without something farting by