The argument for preservationists is strong. Many amiibo, such as the Skylanders Superchargers Bowser or the Animal Crossing Sanrio cards, are out of print. Collectors pay $80+ for a paper card that originally cost $6. Using the key to write a "backup" copy to a blank card occupies a gray area similar to ROM dumping—generally considered legal for personal backup if you own the original, but almost certainly illegal for distribution.
If you are setting up an app to manage amiibos, follow these general steps: Obtain the Files amiibo encryption key
Once published, the floodgates opened. Tools like TagMo (Android), amiitool , and Thenaya let anyone decrypt, modify, and re-encrypt amiibo data on a standard PC or phone. The argument for preservationists is strong