Just a few things
No. Michigan is in the Eighth Circuit, and Wisconsin is in the Seventh Circuit, US Court of Appeals. I believe that it will have to go to SCOTUS to achieve jurisdiction over Wisconsin.
Michigan is in the 6th Circuit. Decisions from other circuits have persuasive not mandatory authority in other circuits. If you mean that only SCOTUS can make an out of circuit decision binding in Wisconsin, you are correct.
This was a state case, not federal. The term circuit refers to the state trial court of general jurisdiction. This case could migrate to the federal system but it ain't there yet.
Others have addressed the impact of the federal GFSZ statute. Pays to have a permit.
Well there still seems to be a dispute. Think of it this way. You have to jump through two hoops to carry in a school zone. Federal and State. The federal hoop says no carry in the zone (school property + 1000 feet) unless you have a permit from the state of interest. It doesn't matter if you are a nonresident if the state issues NR permits. You cannot use an OOSL to carry in a SZ, even if the state says you can. The state hoop - some states like WI took this beautiful federal exception and rendered it meaningless to a great degree by imposing a school property restriction to carry. So in Wisconsin, permit holders are ok in the buffer zone but not on the property. Other states vary. Neither MI nor WI issues nonresident permits so only residents may take advantage of whatever lessened restrictions there are.