I wonder.....
"You" aren't doing it, it's only a dummy.
You can wear a cop outfit for Halloween or a costume party, (or if you are a "dancer") as long as your costume isn't a perfect replica AND youdon't try to pass yourself off as one. But since it is a maniquin it isn't even a person, it's kind of like a cardboard cutout of a cop.
(like the full size plywood "cars" that some cities use for decoys)