I'm not sure who is more stupid, the talking heads that didn't research this, or the dumbass they talked to that said it was legal. Below are excerpts from CA Motor Vehicle Code regarding noise -- there are plenty more, but these seem most applicable.
I should have run for Governor....
27150. (a) Every motor vehicle subject to registration shall at all
times be equipped with an adequate muffler in constant operation and
properly maintained to prevent any excessive or unusual noise, and
no muffler or exhaust system shall be equipped with a cutout, bypass,
or similar device. [whistle????]
27150.1. No person engaged in a business that involves the selling
of motor vehicle exhaust systems, or parts thereof, including, but
not limited to, mufflers, shall offer for sale, sell, or install, a
motor vehicle exhaust system, or part thereof, including, but not
limited to, a muffler, unless it meets the regulations and standards
applicable pursuant to this article. Motor vehicle exhaust systems
or parts thereof include, but are not limited to, nonoriginal exhaust
equipment.
A violation of this section is a misdemeanor. [Fine the idiot that installed it??? "whatever they want I just install it..." Dumbass]
---- My personal favorite, doesn't much more clear than this ---
27151. (a) No person shall modify the exhaust system of a motor
vehicle in a manner which will amplify or increase the noise emitted
by the motor of the vehicle so that the vehicle is not in compliance
with the provisions of Section 27150 or exceeds the noise limits
established for the type of vehicle in Article 2.5 (commencing with
Section 27200). No person shall operate a motor vehicle with an
exhaust system so modified.
27206. For the purposes of Section 27200, the following noise
limits shall apply to any other motor vehicle, not specified in this
article, manufactured:
(1) After 1967, and before 1973 .............................
86 dbA
(2) After 1972, and before 1975 .............................
84 dbA
(3) After 1974 ..............................................
80 dbA
[Specific noise limits apply to vehicles over 6,000 lbs. gross.]