Nope, John Deere (tractors) has been doing it for ages and the farmers are trying to fight it.

https://motherboard.vice.com/en_us/article/pamkqn/watch-trac...

It's entirely legal because all of the rules surrounding the right to repair and maintain cars are related to emissions certifications, which Tesla doesn't have to do... Other car manufacturers, like Nissan, certify their fully electric vehicles as zero emission solely to have them count in their total fleet CAFE standards numbers, but that means that they have to provide warranties, parts, repair manuals, etc. in line with the federal rules. Tesla exists outside that system.

We should be pushing to have the warranties and the safety critical systems parts and repair information covered under the NHTSA safety certification rather than the EPA emissions certification, but that hasn't been necessary until very recently, and honestly, the majority of people willing to buy a Tesla aren't going to work on them, just like the majority of people buying a regular car aren't going to work on them, so it hasn't been a real issue yet. Personally, I wouldn't buy anything that I don't have a legally enforceable guarantee of aftermarket parts, manuals, etc. on because I don't trust any company to actually provide ongoing support, esp. in tech cough google chat services cough. Particularly given the dollar figures involved...

If you're in the US (I'm going by the reference to a lawsuit), then I don't think it is. This is just the way this company does business and in the states they are free to do so.

why would it be illegal?