When I was in law school I was on Law Review. I remember one student who submitted an article for submission and I was was assigned to check the footnotes.
The student lifted just about every word of the article from various law review articles and legal books without attribution. I pointed out to the Dean that this student had pretty much plagiarized the entire article and when he was called on the carpet he threatened to sue me for slander and libel.
I hope that creep never got his bar ticket. But he probably did.
Plagiarism is unethical whether it’s illegal or not. As theft, it should be illegal, but I imagine it would be extremely hard to enforce and also it would be easily abused. However, in the case you cite from your law review days, when huge chunks are clearly lifted from other people, there should be some kind of censure, at a minimum.
Is it possible that different humans could come up with the same “one-liner” over the course of time. I imagine. But not big chunks. I remember driving by a graveyard on the way to church when I was a kid. It was a new graveyard and the had a chain fence around it. I came up with “why did they put a fence around the graveyard? ... people were dying to get in.”
I was like 9 or 10 years old, and had never heard that joke in my life. It was entirely on my own. But, it turns out it is pretty common. Some things aren’t as original as we might think.
But, I didn’t come up with the Gettysburg Address independently on the way to church. It would be impossible.