It's my understanding that in the past, things have lapsed into the public domain as copyright expired. However, laws changed, and these public domain items were put back under copyright protection. I cannot remember where I read it, or under what context.

That being said, what I said was, afaik, incorrect. If something is specially put into the public domain, it's there. The things I read about weren't explicitly put into the public domain by the copyright owner. They just fell out of copyright.

My apologies.