As mentioned by BigAl07, it's hard to tell from a video and be positive about anything in regards to whether or not the flight is legal, but right off the bat (assuming the PIC is at least 107 and even assuming he is flying a Mini in Cat 1 operations) these
might be some reasons the flight could be illegal.
No person may:
(a) Operate a small unmanned aircraft system in a careless or reckless manner so as to endanger the life or property of another; or
(b) Allow an object to be dropped from a small unmanned aircraft in a manner that creates an undue hazard to persons or property.
No person may operate a small unmanned aircraft over a human being unless -
(a) That human being is directly participating in the operation of the small unmanned aircraft;
(b) That human being is located under a covered structure or inside a stationary vehicle that can provide reasonable protection from a falling small unmanned aircraft; or
(c) The operation meets the requirements of at least one of the operational categories specified in
subpart D of this part.
To conduct Category 1 operations -
(a) A remote pilot in command must use a small unmanned aircraft that -
(1) Weighs 0.55 pounds or less on takeoff and throughout the duration of each operation under Category 1, including everything that is on board or otherwise attached to the aircraft; and
(2) Does not contain any exposed rotating parts that would lacerate human skin upon impact with a human being.
(b) No remote pilot in command may operate a small unmanned aircraft in sustained flight over open-air assemblies of human beings unless the operation meets the requirements of either
§ 89.110 or
§ 89.115(a) of this chapter.
No person may operate a small unmanned aircraft over a human being located inside a moving vehicle unless the following conditions are met:
(a) The operation occurs in accordance with
§ 107.110 for Category 1 operations;
§ 107.115 for Category 2 operations;
§ 107.125 for Category 3 operations; or
§ 107.140 for Category 4 operations.
(b) For an operation under Category 1, Category 2, or Category 3, the small unmanned aircraft, throughout the operation -
(1) Must remain within or over a closed- or restricted-access site, and all human beings located inside a moving vehicle within the closed- or restricted-access site must be on notice that a small unmanned aircraft may fly over them; or
(2) Must not maintain sustained flight over moving vehicles.
(c) For a Category 4 operation, the small unmanned aircraft must -
(1) Have an airworthiness certificate issued under
part 21 of this chapter.
(2) Be operated in accordance with the operating limitations specified in the approved Flight Manual or as otherwise specified by the Administrator. The operating limitations must not prohibit operations over human beings located inside moving vehicles.