With the Metroid's (NES) 30th anniversary, what a better gift for us than the release of an anticipated remake of the legendary Metroid 2 for GameBoy? But as it seems, Nintendo, which holds the rights, puts a brake on the fans' joy.
So, when the game completed and was freely available online, Nintendo hunted all the companies and pages where the file was hosted to stop its sharing.
Friends: Nintendo has hit us (meaning, our website host) with a DMCA takedown notice. We can no longer host the AM2R file. Sorry!— Metroid Database 🌐 (@MetroidDatabase) August 7, 2016
Many similar fans' efforts have found Nintendo's legal 'wall', such as the Super Mario 64 HD, as well as the effort of archive.org to make the Nintendo Power, the first magazine for NES magazine by Nintendo America, available online.
However, in this reddit thread you can find more information and magnet links for the game.