The emulator is already freely available to download and install across a range of devices, but the Steam release would have provided a more convenient install path and due to its presence on the Steam Store, it likely would have also raised the popularity of the emulator.
Now as reported
by PCGamer, Nintendo has issued DMCA copyright takedown notices against Valve to force them to remove the emulator from Steam. Currently, it doesn't appear that other emulators like RetroArch have been impacted.
In a post on the
Dolphin website, the team confirms the DMCA and adds that the emulator's Steam release has been “indefinitely postponed” while they “investigate” their legal options. Emulators have long existed in a legal grey area, in part due to their association with piracy.