Let's see if I can put the history together as I've grown to understand it regarding forest roads. Note a forest road is any pathway that you can get an unassisted Public Act 300 vehicle through (ie get a full size 2wd car through). This road is not part of the county or state road system; it's difficult to discern between such roads in some areas although county's are supposed to have stop signs and road names (or seasonal road signs) on their roads. Generally speaking the road must be greater than 50" since it would be a "trail" if it were less than that.
On to my rambling..
Back in the lates 70's they came up with an ORV plan. Part of that plan was to put 1500 miles of single track on the ground, mark it, certify it and then go to closed unless posted open. This meant we would have 1500 miles of single track plus all of the forest roads, which sounds like a decent deal, albeit "not closed" would be even better for some of us (some of us have too much now). Keep in mind this is just for the ORV population in the late 70's, four wheelers weren't even in the picture then.
A good 10 years later a higher up mucky muck (DNR, I believe) noticed that the plan was still not implemented and lit the fire under somebody's tush.
They then started marking trail. This irked some clubs 'cause their event trail was the only trail available for (whomever, DNR most likely) to mark in for designated trail. It was a rush job in some respects but a huge job to begin with and when that's taken into account, it was handled pretty decently. Some of that lost event trail still causes unrest between the CCC and one or more clubs (why, not sure, guess the CCC was an easy to blame target at the time). Back to the topic. It took a couple years, but they marked and certified (as in "yeah, I rode it and there were x miles of marked trail") the required 1500 miles.
I don't recall off hand what the ORV Route status was at the time nor how maintenance specs fall into this along the way. Routes were supposed to be of value, making connections & going places but they frequently had to use county roads. This was OK until the counties found out they could be sued because of ORV travel on their roads & naturally the counties opted not to have Routes use their roads. Legislation was passed several years later that gives them tort immunity (think that's the correct term) for allowing ORV travel on their roads, similar to snowmobiles being allowed, but they have not gone back to "reconnect" the routes.
Back to the ORV Plan & stuff. They had the miles down, then they needed legislation & funding for education, maintenance, enforcement, restoration (uck) and so on. That's where the ORV stickers came from and I'm guessing that since it was to fund DNR programs they opted at the time to get the Secretary of State out of the picture and administer the program themselves (no sharing of the pie, I suppose). From this perspective, it makes sense for me anyway.
After much gnashing of teeth they decided it was good and so it shall be. No more open trails unless it has a triangle on it; forest roads are still open (important note). For the topic of this discussion it's not as relevant but still good to know - event trail was also on the list of things we "had"; there would be the regular trail and when you wanted an event (enduro, trail tour) you would get to use temporary event trail which would save the beating on the public trail and give riders something new & different.
Seems like it was around '92 when this was finally being enforced although it went live in 90 or 91. And people were p|ssed off 'cause they couldn't ride where they used to, nor camp there either 'cause no trail was close to them (my crowd) but life moved on and the trails survived although the traffic on them was greatly increased.
Soon after this happened, a higher up in the MUCC decided he no longer wanted ORVs to be on the forest roads. Seems some of them were driving through or near his property or fishing creek - the way it's told by several sources to me is that a retired AF captain/pilot from up near Oscoda was PO'd 'cause ATVs were driving through his trout fishing crick. He also happened to be way high up in the MUCC at the time. Don't know his name, and this last bit is all "as it's been told". I'm certain there were other factors involved and this is not the "whole" story.
So, this dude makes it his personal mission to shut the forest roads down, shut all of it down if possible, but settle for closing of the forest roads. The MUCC has the muscle to pull this off and through their membership's influence they got legislation passed to close the forest roads down (circa 1994).
Ironically the MUCC would probably be the greatest benefactors of open forest roads - their hunting members in particular. I've understood their position has changed over the years to be more in favor of opening those roads back up, although the DNR is adamantly opposed to it. If we joined forces with the MUCC, there's a chance we could get the roads open, but it would be a huge task.
That's my story & I'm sticking to it, unless somebody has a different view. ;-)
Most of this has been independently gathered from different sources and the gist of it stays the same between those stories. I was not personally involved in the sport at this level back then (I was just a punk rider).