Illinois is mandatory via the phone, replaces the check stations that were around in years past.. What is to stop someone from calling in a buck and saying it was a doe? Well, there is always the random chance that they will send a CPO out to your house to take a look. I can't remember how it is being done but it is the same thing as everything else. What keeps me from putting bait piles out or salt licks? Having 6 rounds in the shotgun instead of 3 (Or is it 4?) during shot gun season? The chances of getting caught doing any of these are negligable at best.. But, all you have to do is tick one person off and they turn you in or make a tip to the DNR and all of the sudden you get caught.. Or, what keeps me from doing any of these things is, well, I tend to follow game laws.