So, imagine you're running a free service as a side project. And the state of Idaho introduces a law, that has federal teeth, such that if a resident of Idaho might use your service, you must register with the state of Idaho. Would you be happy about that? Is there any possibility that you might decide to simply block Idaho rather than deal with the hassle?

A better solution would be a webpage, hosted by the state of Idaho saying "Here's what we're after, don't do these things, and you're in no danger." Followed, hopefully, by a list of things that you weren't planning on doing anyway because you're not a jerk, and that are crystal clear so you don't have to speculate about how selective the attorney general of the state of Idaho is in prosecuting these sorts of crimes.