What is a Uniform?

So a bus driver slugged McGruff. A blog of which I am quite fond, Holy Prepuce. has the story

Brim was later charged with simple assault on McGruff's human occupant, D.C. Police Officer Tyrone Hardy. The decision to charge simple assault, rather than assault on a police officer, raises an interesting legal question: to commit "APO" in most jurisdictions, the defendant must know that the victim is a police officer. Does socking McGruff the Crime Dog count? The person inhabiting McGruff turned out to be a real-life police officer, but the role could as easily be played by a civilian. Except where the victim is a plainclothes officer, the knowledge element of APO is usually open-and-shut because of the police uniform. Would McGruff's oversize blues count? The government's restraint in charging Brim means we'll never know--at least not until the next McGruff beat-down.

Makes me wonder if Smokey the bear counts as an authority or at least a park ranger in various wilderness and camp settings. Also if Captain Morgan can perform weddings, at least in Vegas or something.