Since when is it illegal to connect to it if they leave it wide open? What's the point of locking your WiFi network then if it's illegal? It's not that hard to clone a MAC address but if your not smart enough to lock down your WiFi then that's your problem
Perhaps you need to educate yourself with the Computer Fraud and Abuse Act that does say that connecting to open wifi without permission is illegal. On top of that, gaining access by spoofing a MAC address is illegal too.
IOWA § 716A.1 Definitions § 716A.2 Unauthorized access § 716A.3 Computer damage defined § 716A.4 Computer damage in the first degree § 716A.5 Computer damage in the second degree § 716A.6 Computer damage in the third degree § 716A.7 Computer damage in the fourth degree § 716A.8 Computer damage in the fifth degree § 716A.9 Computer theft defined § 716A.10 Computer theft in the first degree § 716A.11 Computer theft in the second degree § 716A.12 Computer theft in the third degree § 716A.13 Computer theft in the fourth degree § 716A.14 Computer theft in the fifth degree § 716A.15 Chapter not exclusive § 716A.16 Printouts admissible as evidence