A brief explanation of torts
As stated earlier, trespassing and other property right laws are torts. Torts are crimes against the rights of an individual. Since trespassing violates a landowner's property rights, the landowner must normally file a complaint against the at-fault party. Only a Landowner or their Agent, can initiate a legal action for trespassing. Many landowners do not realize this and many ask the question "Why don't you just write them a ticket?" DNR officers do not have the authority to carry cases to magistrate's courts on trespassing or other property right crimes on their own without a warrant from the landowner. If the landowner does not care to sign a warrant, no crime has occurred.
There are a number of tort causes of action which might apply to unauthorized entry of land by hunters, including trespass, negligence, conversion (if personal property is stolen), and malicious injury to property. The basis for tort actions is that the owner has been injured and deserves compensation by the wrongdoer. Punitive damages might be available in a proper case to punish the wrongdoer. An owner might also request an injunction preventing the wrongdoer's entry upon land (or near it) in some instances.
Remember, however, that you must not attempt to physically restrain violators, start or invite a confrontation, or behave wrongfully yourself. (If you or other persons are in danger of being shot by hunters who are unaware of your presence, you should notify the hunters of your presence to avoid being injured.) Do not compound the problem by committing a crime for which you may be held responsible.
Another reason to require a landowner to sign warrants is the DNR officer did not see what the landowner observed. Since this may be instrumental in the case, the landowner must swear to these facts under oath in front of a judge. This will assist the judge in determining which, if any, laws (Title 50 and Title 16) have been violated.