Changing your IP address or using proxy servers to access public websites you've been forbidden to visit is a violation of the Computer Fraud and Abuse Act (CFAA), a judge ruled Friday in a case involving Craigslist and 3taps.
Changing IP address to access public website ruled violation of US law | Ars Technica
There is some nuance to the case, for example the judge made a point about "level of notice" i.e. if you get a c&d you know damn well you are not welcome.
Slippery slope.