The USITC notes that while its investigation has begun, it hasn't ruled on the validity of the complaint. The commission will hold an evidentiary hearing to determine whether Nintendo is in violation of the Tariff Act, with a final decision "at the earliest practicable time." The USITC will announce a target date for the end of the investigation within 45 days.
"The products at issue in the investigation are controller systems with parts that attach to two sides of an electronic device, such as a smartphone or tablet, and the parts fit into a user's hands and have gaming controls," the USITC's announcement reads.
Nintendo declined to comment on the investigation. We've reached out to Gamevice and will update this story as we hear back.
This isn't the first time Gamevice and Nintendo have gone head-to-head over the Switch. In August, Gamevice sued Nintendo for violating its Wikipad patents with the Switch, but that lawsuit was dropped in October.
For the record, Gamevice doesn't hold a patent on cardboard-based video game accessories. Nintendo's grip on that market is secure, at least.