Illinois regs are even more restrictive than MO. The client does NOT have the final word. If I get a call from someone with raccoons or possums (etc) hanging around their door at night and crapping all over their sidewalk and deck, that may not be a "wildlife" problem. It is more likely a "human" problem. In almost every one of those cases, the person is leaving pet food out after dark (usually for cats). My regional wildlife biologist is a real stickler for laws..... he will first require the person/people to STOP leaving any food source out after sunset for TWO WEEKS. That will often eliminate the unwanted wildlife visitors. The problem is typically human-caused, not wildlife invasion.
DNR manages the nuisance wildlife program, and a major part of the program is solving problems in conjunction with wildlife conservation. The biologist does not see any reason to kill wild animals when the problem is usually 95% human behavior. Same deal with "seeing" a fox or any animal in the yard..... they are NOT considered a nuisance by DNR. And DNR is not held responsible for wildlife behavior in our state. That's why the zillion law suits filed for auto-deer collisions against the state are never even brought up.
I have no problem with anything other states do, or WCO's in other states as long as regs are being followed. Some will disagree with our biologists regarding habitat or behavior changes as a FIRST attempt, but it is what it is. We can't do squirrel reduction trapping or any other removal UNLESS it is causing physical damage to a structure or is a direct health/safety threat. That doesn't include what an animal "may" do at some point.
On the plus side, having a regional biologist who follows the rules can be beneficial. Those who worry about "not being able to make money" on every call due to our regs should consider; if this biologist finds out a town or city is providing traps to residents for wildlife removal and they don't have a nuisance wildlife permit, he quickly informs them they are breaking the law and shuts them off. Laws are laws..... whether they all make sense or not is not the issue.... following them IS.