A state law cannot recall a US Senator that the US Senate has seated.
Tell that to the Utah legislature. There will be a fight even through the case law has been decided as you say. The bill is in the Utah Legislature despite the way federal law actually is.
If its passed, there likely will be a court case on it.Maybe it will go to SCOTUS, who knows? But the People of Utah want to take the GOP away from exclusive control of the Mormon Church.