You own the Tesla hardware. You do not own the software. You're also not forced to buy one. You're also free to write your own software for the vehicle to bypass Tesla.
While this grey area has generally survived in smaller items, I suspect a car, where you literally have a title to it, is not so defensible under that claim. Especially when they also make it effectively impossible to repair the hardware outside of their company as well.
I thought the problem was that this part was illegal also