A common occurrence in the Wii era was Nintendo being taken to court by various companies claiming that the system violated existing patents. This has happened with multiple Nintendo systems, in truth, with the 3DS also being targeted quite a few times. Nintendo wins the majority of these cases and, even on the rare occasions it loses initially, seems to have the clout to appeal and clear cases in the end.
It's inevitable that the Switch will also be the target of litigation, and it seems that Gamevice is one of the first companies out of the gate. As reported by Engadget, a lawsuit has been launched citing patent violation, namely that the Joy-Con concept is allegedly too similar to the detachable controller and "flexible bridge section" seen in previous Gamevice products. As is the norm in these cases Gamevice wants a substantial settlement and for Switch sales to be stopped.
This refers to two lines that the company has launched over the last few years. First was the Wikipad, a tablet with controller launched in 2013; a tablet would slide and click into a relatively large controller, as you can see below.
That product didn't take off commercially, so more recently Gamevice launched a controller accessory that can clip into smartphones and tablets, as you can see below.
Naturally the courts will determine whether there's a case. We doubt this will be the last such claim, either, as various clip-on controller accessories exist that work with smartphones and tablets; it was the existence of accessories like these that some used as 'evidence' (in the NX days) to argue against the 2016 leaks around a tablet with detachable controllers.
We'll keep an eye out for any updates on the case.