Sort of how a death can result in a manslaughter charge, or various degrees of murder charge (each having different maximum penalties and distinct qualifications).
The specific circumstances can take into account things like:
- Did the defendant aim to profit financially from the actions?
- Was the defendant attempting to cause malicious harm? (i.e. he didn't want to profit, but he was trying to cause damage)
etc. The most innocuous being "no financial gain + no malicious intent."
But accessing an unauthorized system? That term is so ill-defined, that it quite literally means you can be prosecuted for modifying a URL and being given back a web page you weren't supposed to see.
The fact the webserver willingly gave the information I requested to me (did not 403 or 531), so I must be authorized.
You may as well ask, if I wasn't authorized, why did the door open and let me into that stranger's house?