All Roush mufflers are under the volume limit by US regulations with the exception of the off road systems and a few others like the Roush 427R mufflers (they come with the car but "aren't installed" according to Roush). Sneaky, Sneaky..
I don't know about Canada, but I'm pretty sure the only federal US laws about exhaust are tampering with a muffler or catalytic converters, and illegal to have no muffler at all; however, local places (state or community level) have noise requirements, such as Texas can be as loud as they want while California can't be more than 95 decibels at the muffler. In New York City, it's actually illegal for your exhaust to be "plainly audible" from 150 feet away.
I'd check your local and federal laws, look into the specific ticket, and go to court with Roush documents and pictures. I'd also take the car. If he wrote a ticket for no mufflers, you should be off. If he wrote a ticket for illegal muffler or no muffler, then you may be on thin ice depending on local laws.
2007 Mustang GT 302 stroker 6060 swap, 3.73 gears, Hidden Hitch Receiver, Barton Short Throw, JBA LTs, Borla Touring Axle Back, Lito tuned SCT X4. BMR SP009, Bilsteins, J&M CC plates, J&M LCAs. 4 Piston Brembos
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