IANAL, but i would expect that even if that clause of the contract would hold in court (and perhaps even forces the seller to pay some contractual penalty to Te

IANAL, but i would expect that even if that clause of the contract would hold in court (and perhaps even forces the seller to pay some contractual penalty to Tesla for a breach of contract), it would still be illegal for Tesla to tamper with third-party owned car and deactivate it, because Tesla has no contract with the new owner, and the ownership was legally transferred to a third party, even if that transfer was a breach of contract. The point is that the contract is bound to the person who accepted it, not to a property itself (there are exceptions for specific types of contracts on realty).