Every state that I know of requires you contact the game warden and they OK it, give you a tag, etc....

But I've also heard horror stories from a few different states where the authorities claimed it. Seems like that's the case with the real trophies.

Here in PA, if you hit a deer with your car, you call the game commission and they issue you a possession tag. Then you keep the deer. UNLESS IT'S A BUCK. Then the game commission takes it. But, you can buy it back from them at $10 per point.
$20 for a spike, $100 for a 10 pointer, etc... Stupid rule.