Well, "industrial espionage" actually is a crime since 1996, no matter what tools you use to do it (and notably, has the harshest sentence of the 3 major types of crimes Nosal was charged with).

Unauthorized access to a computer network was made to help complete the crime, which is itself criminal, just like there is a charge "mail fraud" that makes use of the postal system to further any criminal act illegal.

Conspiracy is always illegal itself as well.