Here is a quick lowdown. Go to the USFS Okanogan/Wenatchee National Forest page. Their search bar leaves much to be desired. Had to look thru 3 items and found this.
The restrictions apply the 4wheel drive vehicles only. Quads and Motorcycles may go either direction on the trail.
When I get time I can find and scan the order but in jest this explains it.
Normally the order is posted at the kiosk at the beginning of the trail. In the past it has been torn down. However the order is also posted on the kiosk at the end of the trail on the FS 1500 road. All Forest Orders are available for viewing at the District office during business hours M-F. You can also find some info at the District Office in the entry foyer it is open 24/7.