http://www.michigan.gov/dnr/0,1607,7-153-10365-95931--,00.html
NO firewood over the bridge. Primarily to prevent the transfer of eggs and larva of EAB (emerald ash borer), but NOT just EAB...but other diseases and nasty stuff can be spread around too.
You would feel like a heal if you introduced something by doing so, and so it is best to simply spend a few more dollars and buy the wood locally.
Your wallet will hurt some, but you will rest better knowing you didn't contribute to thousands or millions of trees being infected or killed eh?
Just don't do it!!
BTW you can NOT take any ash into any state campgrounds....not sure why since they have now created this mess, might as well burn as much as you can...there are whole forests in SE Michigan that are leafless and deader than heck...it is truly a sad thing to witness. For the most part this was all preventable had we taken the proper precautions. we didn't and now we live with what has happened to a single species of trees.