The problem with your diatribe is the computer did not belong to the individual - it belonged to AO&GCC. Like it or not, there is no expectation of privacy when using your employer's computer. The files therein legally belong to the company, not to the individual. As such, Palin, as an employee of AO&GCC, had full legal authority to access the AO&GCC computer, even if the prior employee had not left. That it was at the request of the AG just ices the cake.
Also, there is no legal expectation to privacy if using an email system which belongs to a tax supported organization. Those files are considered public property because the email system itself is paid for with tax (public) money. While the average Joe cannot go into City Hall and demand to see all the email from the last month, (though you CAN do so in school districts, believe it or not) the law provides that no warrant is needed for access, and officials in charge of the organization have authority to give access to such files without the user's permission.
OTOH, email accounts belonging to an individual on a private email system DO have an expectation of privacy, and hacking them IS illegal, publishing the content of a private account without permission is illegal, etc.