Classified docuements have a long history in the Republic. For millenia there has been times in great strife and war that it was necessary for the Republic to keep things secretive, for example battle plans during the Mandalorian Wars, or during the wars with the Sith. Of course this has led to corruption within the Republic as the years have passed by. Under the Emperor we have a clear system of obtaining this information. A simple request through the Holonet will yield you information. The Empire however does retain the right to guard secrets that would endanger the lives of those proud men and women serving in the Army and Navy. However, without the threat of corruption that the Old Republic possess, these secrets only pertain to those where security is at risk, or could be used by the Rebels in their fruitless pursuit of tearing down the security the Galactic Empire has garnered us.