Under US copyright law, a library or archive may copy software for preservation if the original format is obsolete (e.g., floppy disks or original NES cartridges that can no longer be manufactured). Archive.org argues that the NES is obsolete.
: Files are typically stored in the .nes (iNES) format, which includes the game's code and information about the cartridge's hardware. All Nes Roms Archive.org