Not legality per se I don't think but rather terms of use in some places I would imagine?

If for instance you drove through one of those fast track EZ-Pass toll lanes with no gates or used a toll road with gantry readers instead of toll booths and your EZ-pass didn't register properly then the procedure is to look up your license plate and either deduct the balance from your EZ-pass account or send a bill to the address on the account that it's registered to if there is insufficient funds. The agency may have to jump through more hoops if the license plate isn't registered to an account (a rental for example) and they'd need to ask the DMV for the address of the owner, especially if it was an out of state license plate.