^ It's not that it's emissions, it's that it's illegal to do a muffler delete in most if not all 50 states, or a threshold noise level consideration, possibly to address that some vehicles have multiple mufflers or so-called resonators. Washington DC is not a state tho', so not sure how law enforcement would address it. Code:
Washington D.C.
D.C. Mun. Regs. Tit. 20
§ 2812 ALTERATION OF MOTOR VEHICLE EXHAUST SYSTEM
2812.1 No person shall modify or alter the exhaust system of a motor vehicle or motorcycle in a manner that will amplify or increase the noise emitted by the vehicle above the level permitted under § 2811 of this chapter.
2812.2 No person shall use or operate a motor vehicle or a motorcycle having an exhaust system that has been modified or altered in a manner that will amplify or increase the noise emitted by the vehicle above the level permitted under § 2811 of this chapter.
§ 2811 OPERATIONAL LIMITS FOR MOTOR VEHICLES
2811.1 No person shall operate a motorcycle, motor vehicle, or combination of motor vehicles of a type subject to registration under D.C. Code § 40-103 (1990 Repl. Vol.) at any time, or under any condition of grade, load, acceleration, or deceleration in a manner that exceeds the maximum noise limits designated in the table of this subsection for the specified speed limits, measured at a distance of fifty feet (50 ft.) from the center line of travel by a sound level meter switched to the A-weighting network, in accordance with such nationally recognized test procedures as the administering agency may prescribe in accordance with § § 2700.7 through 2700.9 of Chapter 27 of this subtitle.
(a)Any motor vehicle with a manufacturer's gross vehicle weight rating of ten thousand pounds (10,000 lbs.) or more, and any combination of vehicles towed by that motor vehicle: 35 MPH or less: 86 dB(A) Over 35 MPH: 90 dB(A) Stationary Run-up: 88 dB(a)