U.S. law around the early 19th century would be a pretty decent compromise. https://en.wikipedia.org/wiki/History_of_copyright_law_of_the_United_States#Copyrigh

U.S. law around the early 19th century would be a pretty decent compromise. https://en.wikipedia.org/wiki/History_of_copyright_law_of_the_United_States#Copyright_Act_of_1831 https://en.wikipedia.org/wiki/History_of_copyright_law_of_th... or the 1790 version. Either way, there's a moderate term renewable once if you go to the trouble.