In the US, copyright has been retroactively extended multiple times. Steamboat Willie for example has repeatedly been snatched away from the public domain in the last minute.
It was first due to enter the public domain in 1955. Then in 1986. Then in 2003. Last extension (that I know of) was until 2023 which is the year I write this.
But at the same time, ex post facto laws are expressly forbidden by the United States Constitution.
So how is it possible that ex post facto copyright extensions have been passed multiple times?
As I see it the victim here is the general public. Is it simply that they haven't sued for rights? Or did they?
If I sign a contract that I will hand over my poem to you in two weeks, can I just change my mind and say "no, now it's three months" whenever I feel like it? AFAICT that's exactly what's been happening here.