Brother Paul Harm is right as far as Michigan regs are concerned- it is the Federal reg. that outlawed the 8 gauge gun. Apples to eggplants here- but you can legally use the big "Super-8" on any legal non-migratory game bird in proper season here, you can also use a scoped .300 Win. Magnum rifle for squirrels and rabbits or varmints and vermin, even in the "shotgun only" deer hunting area known as Zone Three by our DNR.
I think an element of practicality might enter the picture. There may have been a few 10 ga. repeaters (the Winchester lever action shotguns) back around 1895-1920, but the 8 gauge shotguns were basically either a single or a double barrel gun- so let's say, for the sake of spirited discussion, a Chesapeake Bay market hunter who added to his income during the waterfowling season used an 8- open choked and with "St. Ouis 3's" lead shot-not cheap to shoot, even reloading- he guides a client who has a Win. M1897 pump- 6-7 shots, shells way cheaper than his 8 ga., easier gun to handle--durable, good pointing for that style of shooting-
What was the national waterfowling picture in 1912-13 when the Weeks Mclean bill passed and the 8 gauge was banned? By then the M 1897, the Browning A-5, some with ten shot extensions, were in usage by market hunters, and the Model 12 was right around the corner- From reading Nash Buckingham's write-up, I guess many of the 8 and 10 bores were used by sportsmen, some of whom (possibly like Nash and his friend Eltinge Warner) wanted to see repeaters banned for waterfowling)--
Today with the National situation as I surmise it: Iraq, Afghanistan, ?? about the economy, the BP Gulf disaster, and the list goes on- to correct a possible error made back in 1912 to allow a small % of the duck hunting fraternity free choice in the gauge and type of weapon they might wish to use- sorry Boys, I am all for the 8 gauge for those who own them and want to use them, any more than a fine Hammer Parker 10 bore or any other vintage firearm that recalls the "good old days" to some of us- But I just don't see it happening.
But rest assured- if I should come across a brother waterfowler in some secluded spot using a 8 ga., even with lead loads- his secret will be safe with me- Maybe he'll have the good taste to be using a Parker!!