The National Park Service will allow guns to be carried under specific guidelines in the Parks.
http://www.washingtonpost.com/wp-dyn/content/story/2010/02/18/ST2010021806456.html

Isle Royale specific information on guns in the Park:

Firearms and other weapons

Legislation: As of February 22 ...

There are no laws that prevent people from having guns on the concession boats of ours, provided they have been given permission by us in advance according to the CFR's. We have a strict policy of no guns aboard the boats period, no permission granted, if they are on board we can and will ...