It all started when we were kids and happily shooting off our Black Cats in South Florida......then the knock on the door. It was the police.

They wanted to confiscate ALL our Black Cats that we had bought at South of the Border when on vacation with our hard earned allowance. After all, he said, fireworks are illegal in this state. Since we did live by the Chief of Police though, the officer kindly let us keep a few to shoot off at a large, nearby park.
Additionally, here's the law
Florida Fireworks Laws
CONSUMER FIREWORKS
Specifically Permitted Devices approved and listed by State Fire Marshal which emit a shower of sparks upon burning, do not contain any explosive compounds, do not detonate or explode, are hand held or ground based, cannot propel themselves through the air, and that contain not more than 100 grams of the chemical compound that produces sparks upon burning. Any device that is not included in the list of approved items is prohibited, except that snakes, small smoke devices, trick noisemakers and certain other novelties may be sold at all other times.
Specifically Prohibited Firecrackers, torpedoes, skyrockets, roman candles, daygo bombs, and any fireworks containing explosive or flammable compounds.
DISPLAY FIREWORKS
Display Permit Apply to local authorities at least 15 days beforedisplay date.
Insurance Required, $500 minimum.
Operator No license specifically required in state law. However, local jurisdiction may require permit.
Why they are everywhere is beyond me. Maybe something about $$$$$, who knows.

I do know the police definitely look the other way. Since WDW is private property though, they can dictate the rules and enforce they.