First, the RISC-V Consortium is an organization (now) based in Switzerland. Second, there is literally nothing anyone can do to stop you from making a RISC-V core, short of calling it "RISC-V". For that, you have to pass a few tests, but all trivial stuff for a serious contender.

On a related note, I don't think it's an accident that Apple almost completely avoids talking about "Arm" but instead calls it "Apple Silicon".