The anticipated Universal Emulator, which allows users to play emulated games on their Windows 10 devices, made by the developer of NesBox, was approved on the Xbox One but you can't play any Nintendo games on your Microsoft console because it got unapproved again.
The developer tweeted out that the emulator has passed the certification for the Xbox One (via TechRadar):
— NESBOX (@nesboxcom) September 9, 2016
Just as the tweet said, the emulator did pop-up in the store but got removed shortly after (via Windows Central):
Microsoft says: "Your product was unpublished globally or from specific markets". They want me to remove xbox platform support and republish
— NESBOX (@nesboxcom) September 10, 2016
Microsoft, unfortunately, didn't allow the app on the Xbox Store because in their opinion it isn't an app. It falls under the games category, or more specifically under the "primarily gaming experiences" tag, and therefore needs to be approved through the [email protected] program:
Apps that are targeted to Xbox One and are primarily gaming experiences must be approved through the [email protected] Program.
The app will still be available on HoloLens, PC, Phone and Surface Hub after the developer resubmits the app, however, the NesBox developer is working on a workaround for the Xbox by using a web page that would emulate the games inside the Edge browser.
Emulators themselves are not illegal, but the way games are acquired is. The ROM's you need for the emulators fall under piracy and Microsoft doesn't want Nintendo lawyers calling them three times a day.