I'd read the mn dnr fishing regulations book..... here's some info from it:
Shelters (fish houses and dark houses)
The following regulations apply to all shelters used on all Minnesota
waters, unless otherwise noted elsewhere in this booklet.
All shelters placed on the ice of Minnesota waters must have either the
(1) complete name and address, (2) drivers license number, or (3) the
nine-digit Minnesota DNR number on the license of the owner plainly
and legibly displayed on the outside in letters, and figures at least 2 inches in height.
A shelter may not be left unattended anytime between midnight and one
hour prior to sunrise unless the shelter is licensed.
Note: The Dept. of Public Safety - DVS requires trailers used to haul fish
houses or dark houses and enclosed trailers or recreational trailers used
for fishing to be registered. See your local Deputy Registrar for trailer
registration.
A tag, furnished with a license, must be attached to the exterior in a
readily visible location.
Shelters left on the ice overnight need to have at least 2 square inches
of reflective material on each side of the house.
No person may erect a shelter within 10 feet of an existing shelter.
A shelter license is not required on border waters with WI, IA, ND, and SD.
Shelters must comply with the identification requirements of the state
for which the angler is licensed.
Shelters may be used for fishing within the Boundary Waters Canoe
Area Wilderness (BWCAW), but must be removed from the ice each
night. The structure must be removed from the BWCAW each time the
occupant leaves the BWCAW.