We don't have a blanket law against reading other people's messages. The law on intercepting postal mail sent through the postal service does not apply to internet packets in radio transmissions. The judge can't extract the intent of that law and apply it to a different domain. If that was how our legal system worked, you could be stripped of your drivers license for playing a racing video game in your living room while drunk.
You have an argument for why intercepting others' wifi messages might be unethical, but not why it's illegal.
You have an argument for why intercepting others' wifi messages might be unethical, but not why it's illegal.