From a legal standpoint, downloading an NSP for a game you do not own is a violation of copyright law. While some argue for "digital backup" rights, most EULAs (End User License Agreements) explicitly forbid the extraction or distribution of game files. Furthermore, there is the impact on the industry. While

Downloading NSP files for free ("Gratis") is a violation of copyright law. Nintendo is known for being extremely protective of its intellectual property and frequently takes down sites hosting these files.

The search term implies a simple process: download a file and play. In reality, playing a downloaded NSP file of Pokémon Sword requires significant hardware modifications.