I disagree.
If I call your phone and one day you don't answer and I try from a different phone number and you do I think you are ok to have me call you.
Had they notified him with a web page that his mac address wasn't welcome it would have been a different matter altogether.
What Aaron did was the equivalent of trying a different laptop to see if things resumed working.
The very first time that happens, maybe he could have thought it was a network error.
But Aaron kept on evading every single countermeasure MIT was putting in his place. By the time you get to going into a wiring closet, you have well passed the point where you know you are no longer welcome on the network.
The law cares very little about what tools you use, and they care a lot more about the actions you do and why you do them.
Aaron wasn't an idiot. He knew MIT was trying to keep him off. It wasn't just a network error.
Yeah, if they had just blocked his mac address then he could reasonably think "hmmm, I can't connect with this mac address, I'll try a different one" instead of "I am no longer authorized". But if you have to keep reconnecting with different IP addresses and mac addresses over and over again, and finally resort to connecting directly to a wiring closet, then the message is pretty clear that you (not just your mac address) are no longer allowed on the network.
It's clear that someone doesn't want you to have easy access, but it by no means gives a clear message that you aren't 'allowed'. If I set up a wifi portal that flips images upside down and misspells words and all that fun stuff it's clear that your access is being diminished but by no means says I want you off my network.
Calling someone isn't considered analogous to trespassing, while accessing someone's network is. I don't think that's a meaningless distinction at the technical level either. Calling someone is like issuing an HTTP GET on a public server. Putting a computer on their network is something quite different.
As for whether banning they MAC address conveys revocation of the license. The precise form of the communication is irrelevant, it's about whether it can be expected to get the message across in context. Do you think Aaron didn't know, after the various measures MIT took, that he was no longer welcome on the network? If he did know, then the message was conveyed.
You're basically attacking a straw man. You're acting like he was charged for trying to access the publicly-available MIT home page, getting a 404, and trying again with a different laptop to see if the problem was on his end. That's what would be analogous to your "calling someone who isn't answering then trying a different phone" example.
Had they notified him with a web page that his mac address wasn't welcome it would have been a different matter altogether.
What Aaron did was the equivalent of trying a different laptop to see if things resumed working.