Everyone aways references the Magnuson-Moss Warranty Act and Aftermarket Parts.
https://automotiveaftermarket.org/ma...-warranty-act/
I'm not a lawyer but I believe the "intent" the act was to say you don't have buy a BMW oil filter instead of a Fram.
The tune reprogrammed the car. It's not a "part" so not sure how that will work out.
Also not sure if this law applies in CA?
Good luck, let us know how it goes.