At that same link is an account of the unlawful activity. He was not authorized to access a restricted area, set up a sieve on the network, and collect the contents of JSTOR for outside distribution.
He wasn't authorised to access the wiring closet. There are many troubling things about the case, but it's fairly clear Aaron knew he was doing something he wasn't authorised to do.
> He wasn't authorised to access the wiring closet.
For which MIT can certainly have a) locked the door and b) trespassed him, but that's a very different issue than having authorization to access JSTOR.
He didn't do it without authorization.
https://en.wikipedia.org/wiki/Aaron_Swartz
> Visitors to MIT's "open campus" were authorized to access JSTOR through its network.