I'm not a lawyer or an expert, but looking at the Wikipedia page for the DMCA [0] there appears to be protection for retro games:
"An exemption was made for 'Computer programs and video games distributed in formats that have become obsolete and which require the original media or hardware as a condition of access.'"
EDIT: Actually archive.org posted an article about exactly this [1]
[0]: https://en.m.wikipedia.org/wiki/Digital_Millennium_Copyright...