now you could say that DeCSS was a protected exercise in reverse engineering, but it involved taking information belonging to others (the decryption keys) and sharing it in ways that broke the terms of the license.
(if you think that it didn’t break the terms of the license, or that the license doesn’t apply in this case, then we’re just debating exactly which numbers should be illegal and which shouldn’t).
later people broken the encryption without using those keys, and distributing these later programs is entirely legitimate (in my opinion) as they really could be developed via a clean room implementation that doesn’t involve accessing any of the copyright protected information at all.
Do you agree to any licensing deal when purchasing a DVD player? I know for sure that I disregard any EULA that I am not presented with before money has changed hands.