Unfortunately for those wanting to play Super Mario 64 on their Xbox One, Microsoft has now officially banned emulators from appearing on the Xbox Store. Furthermore, Microsoft has also removed emulators from the Windows Store as well, enacting new policies that directly target such products.
These policies went into effect March 29th, but the new rules don't appear on Windows 10 devices until users download the Creators Edition patch. While most people will remain unaffected by these changes, anyone that sells emulators will no longer be able to do so, and any products they currently have listed will be delisted.
These new policies will have a bigger impact on Windows 10 than on Xbox One, since it appears as though there were more emulators available through the Windows Store than on Xbox One. In fact, the Xbox One Store has been almost completely devoid of emulators since it came online in 2013, with one notable exception being the Win64e10 emulator, which allowed people to play Nintendo 64 games on their Xbox One. Unsurprisingly, the Win64e10 Nintendo 64 emulator was removed from the Xbox Store not long after it was available to download.
Since Microsoft was quick to remove the Nintendo 64 emulator from the Xbox Store, its decision to outright ban emulators from the console makes sense. After all, Microsoft clearly does not want emulators to be sold through its digital marketplace, and since it will just remove them anyway, it seems like banning them outright will save the company some time.
While some may be disappointed that they can no longer download emulators for Xbox One or Windows 10, they couldn't have expected emulators to stay on the stores. If Microsoft allowed Nintendo games to be played on Xbox One through emulators, it could create complicated legal troubles for the company, so it's hard to blame it for taking this stance and deciding to ban emulators from its digital storefronts.
If emulators somehow become prevalent on other digital marketplaces, like the PlayStation Store or the Nintendo eShop, expect those companies to take similar steps as Microsoft. For now, those that want to utilize emulators and illegal ROMs will still find a way to do so, even if it means they can't do it directly on their Xbox One or through the Windows Store.