Errr, incorrect young padawan. The erase button (if it functions by writing over existing audio, which I believe it does) would completely destroy the audio recording. The CVR in the CRJ is a magnetic tape sound recording format which is nothing like a computer hard drive or other digital storage devices. In the CVR's case, it records audio onto Ferric Oxide and Cobalt coated tape in an analog format. True, there is never a way to completely 100% destroy recorded audio. Theoretically every conversation ever recorded on a 30 minute CVR infiniloop is never 100% destroyed, but it is virtually unreadable. I would venture to say in the 99.99% range.

In other words, unless your company plans to send the CVR to an FBI audiologist and spend hundreds of thousands of dollars and months of time retrieving overdubbed audio, you're probably pretty safe hitting the erase button. So really, the button does do something. Now whether it's legal or not...