They should lose their seats if they don't follow the law. Lucky though, if he loses at the MN Court of Appeals, and State Supreme he can take it to Federal Court, and those Judges aren't elected....
I do agree once it's overturned the DA will likely offer a plea and not have a re-trial.
Actually federal judges give great deference to the opinion of the states highest court as to overseeing their court system. Such as when the Texas supreme court allowed a death sentence to stand where the guys lawyer was constantly falling asleep during the trial.
A federal judge threw out the conviction, but on appeal it was ultimately reinstated by the US supreme court, who relying on the Texas court said there was no proof given, that what the lawyer slept through would have changed the outcome of the case.