From a strict legal standpoint, downloading copyrighted ROMs—even for games that are no longer actively sold or supported by the original manufacturer—constitutes copyright infringement in many jurisdictions. Nintendo has historically maintained a strict zero-tolerance policy regarding the distribution of its intellectual property.
Nintendo shipped every 3DS game cartridge and digital download with a unique encryption key. A standard, .3ds or .cia file will not run on the popular Citra emulator or modified hardware without a separate key file ( aes_keys.txt ). archive.org 3ds decrypted
Games are usually formatted using standard preservation tags: A standard,
Because physical 3DS media is susceptible to "bit rot" (the chemical and physical degradation of cartridges) and the official digital storefront is dead, many archivists view uploading decrypted sets to Archive.org as an act of historical preservation. The Reality of "Redump" and "No-Intro" Collections From a strict legal standpoint