The 13-count superseding indictment (now dismissed) against Aaron Swartz basically boiled down to two major complaints: he accessed a computer system, and then downloaded files, without permission to do either.
It was not completely unprecedented in the pre-digital age to penalize acts that at their essence were about doing something without permission. Trespass, for instance, can be criminally prosecuted if someone has entered another’s real property without their permission. But (per the Model Penal Code § 221.2) it is typically prosecuted as a petty misdemeanor, commensurate with the negligible resulting harm. In instances where more serious harm resulted, a harm that could be properly measured in real word dimensions, such as the deprivation or destruction of real or immovable property, then a separate crime could be charged, such as theft – one targeted to address that violent sort of outcome. But even in those cases the crime and its commensurate penalty would hinge on the resulting harm, not the underlying lack of permission (see, e.g., Model Penal Code explanatory note §§ Sections 220.1-220.3). On its own, merely doing something without permission has not been something US law has sought to punish with serious charges carrying lengthy prison sentences.
In Aaron Swartz’s case, however, while his actions, even if true as alleged, resulted in no more measureable harm than an ordinary trespass would have, he was nonetheless charged with multiple felonies.