No law enforcement officer can go into a home without probably cause, nor can they search a home without a search warrant unless given permission. There are some exceptions based on circumstances, but a DNR officer just can't knock on your door and demand to look in your freezer just because he knows you like to hunt and wants to see if you're in possession of game you're not supposed to have. He'd be free to ask for permission to search, but under the 4th Amendment you can legally refuse and require him to get a warrant. Private land, on the other hand, falls into the same category as a driveway or front porch. Not only is it "plain sight," so discovery of evidence in plain sight isn't considered a search under the 4th Amendment because there is no "reasonable expectation of privacy", but trespassing statutes do not apply to a LEO in the lawful conduct of his duties. For a DNR officer, this includes any area where hunting, trapping, fishing or any other activity that is covered under his state's Dept. of Natural Resources (or similar) authority occurs.

Mike