Michigan's attorney general, Dana Nessel, pre-warned Trump in writing to make sure to wear a mask when visiting any Michigan factory, specifying that it was a legal requirement and also his moral obligation to protect factory workers.
In Trump's defense, he wore a mask and goggles during most of the tour. However, in violation of Michigan law, he took off that equipment before being questioned by reporters, while still at that factory, because he "didn't want to give the press the pleasure of seeing him in a mask". Meanwhile all the factory executives wore such masks.
So, the AG ruled, that he is no longer welcomed back into Michigan. She say that it's obvious, that "Trump doesn't care about anyone, other than himself". "It's disappointing" and she "is embarrassed to have him as president".