Absolutely untrue. In the US, the law is written such that you may only legally access a system that you own or have explicit authorization from the owner to access. It mirrors common law where you're not generally allowed to enter someone else's home even if they leave the door unlocked.
You can, of course (and plenty of people do), debate the specific application of the word, "access" in the context of computer networks.
You can, of course (and plenty of people do), debate the specific application of the word, "access" in the context of computer networks.