When you are camping in Michigan next year, you may have to purchase your firewood onsite at the campground.  Bringing your own firewood to a campsite is already frowned upon, but it's not illegal.

Campgrounds around the state always prefer for you to use wood you find or purchase on the premises to curb destructive invasive species.  It's not necessarily the wood that is the issue (although some diseases like Oak Wilt and Beech Bark disease could cause problems), but rather the insects that live inside.

The DNR is currently working on a new policy for state parks that could make it illegal to bring firewood to your campsite.  The Holland Sentinel reports that "This process will take about two months and a new policy could be finalized in the fall, effective 2018."

An organization called Don't Move Firewood explains reasons for not transporting wood as well as giving suggestions on where to find firewood, rules for specific state parks in Michigan and other general information.