The DMCA explicitly says you're allowed to do this sort of thing for interoperability. IP law is very complicated. Really, as long as you have a license for the

The DMCA explicitly says you're allowed to do this sort of thing for interoperability. IP law is very complicated. Really, as long as you have a license for the game this doesn't seem like it ought to be any different from time-shifting with a VCR. You buy an N64, you buy the game. You copy the game to another medium, decompile it, make it work on a different machine. Your N64 and the original cartridge are inoperable due to age but your license is still good. This does not give you a license to distribute, but at the same time the law is somewhat contradictory on this point, and it makes sense that it is contradictory because it's obvious that a strict interpretation would make it practically impossible for anyone to retain the license to the game, and the license is supposed to be perpetual. Nintendo of course, wants to "sell" you the same game more than once, but it's also obvious that this is not consistent with the intent of the law.