Deleting files on your laptop is illegal?

Yikes. Corporations get yet another court decision against employees. Recently, a judge supported a corporation who is pressing charges against an employee who deleted files off of his laptop, even though the agreement with the corporation explicitly required the employee to "return or destroy" the data in the laptop when he leaves the company. Apparently, they wanted to sue him for going to work for the competition, and tried undeleting files on the returned laptop to go fishing for things to punish him for.

The reason, apparently, that this flies legally is because there is a provision in the Computer Fraud and Abuse Act that makes it illegal to "cause a transmission" and thus "knowingly cause damage without authorization" to a networked computer, and the judge took the view that deleting a file constitutes "damage" to the computer, and typing on the keyboard constituted a "transmission." Apparently, I issue transmissions to damage my computer every day.

Moreover, the judge ruled that the "authorization" provision was violated when the employee had a "breach of his duty of loyalty." In other words, whether or not you can delete a file at work is based on whether or not the company would want that file, even if the reason they want that file is not for business-related purposes but simply to find something to sue you for. And apparently, this is true even though the company explicitly gave him permission to destroy the data on the laptop, indeed required him to do it in a legal document. Moreover, if that contract had said only to "destroy" the data on the laptop when it is returned to the company, instead of "destroy or return," then he would have been liable either way - for destroying or not destroying the data on the laptop - a legal catch-22.

One wonders, then, what the distinction between this and it being illegal to securely delete, say, personal emails. If any. If your employer would like to keep that data, regardless of motivation (and what corporation would willingly give up rights to any content?), does that mean you are in breach of your "duty of loyalty" if you don't want them to keep that data? And given this ruling, it is unlikely to have the analysis of the situation continue to reside with the owner of the actual hardware - more likely, the focus is the data on the computer. Does this mean that if you use a personal laptop for work, then you don't have the right to delete files off of your own computer?