Aftermarket Catalytic convertor installed by auto shop in California - what now? on 2001 Honda Civic

I have a 2001 Civic EX (173000 miles) in California and had got my Check Engine light inspected at a local repair shop. The car had 2 codes P1457 and P0420... the mechanic said that the Catalytic Convertor was bad and needed replacement (in addition to some 3-way purge valve in the EVAP system).. He quoted a price of $400 for the cat (parts + labor) and I asked him to repair. However, he installed an aftermarket Catalytic converter (without my knowledge) and mentioned it only when I went to take my car back as a matter-of-fact FYI statement. I didn't know the implications, but on coming home and reading up some stuff online, I realised that aftermarket catalytic convertors are not legal in California and can also cause issues with smog checks in the future. I'm not sure what my options are and what exactly should I be doing. Pls help!

Asked by for the 2001 Honda Civic
Keep all receipts and repair records!Not all aftermarket converters are illegal for use in Ca. For the money you saved on the converter , it might be worth explaining to a dealer and asking to scan now and monitor converter function and avoid the worry if it's fine.
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California does have strict standards on converters. However most reputable aftermarket companies do comply with the California standards. The warranty on the converter is also federally mandated. Assuming your car is repaired I wouldn't worry about it at this time. BTW to have a factory converter installed would cost you over $1000.