Corrected entry: A signed document is not legal if it can be proven that it was signed under duress. I would say having a room full of people pointing guns at you would be considered duress. The instrument of abdication Queen Elizabeth II signed would never have been accepted as a binding document.
Corrected entry: At the end of the film, when Rowan and Natalie are about to kiss, Natalie is wearing a black dress, but when she is ejected into the air her dress is white. (00:33:45)
Correction: When they're in the car you can only see the neck of her dress and it is white.
Corrected entry: The Queen abdicates, and the next person in line for the throne is Pascal Sauvage? What about Prince Charles, who is next in line, or William and Harry, who are second and third in line?
Correction: The abdication she signs states that she abdicates her family's claim to the throne of England, which would include Charles and William, etc...
Corrected entry: Even though Johnny carries a gun in the movie, he never actually succeeds in firing it.
Corrected entry: When Johnny and Bough find the two sidekicks with the crown jewels there is a mistake. As one of the sidekicks puts the coffin into the hearse and gets into the car, he is the only person in the car. The scene then cuts to the car driving out of the building and the two sidekicks can be seen. (00:21:30)
Correction: Just because we don't see them both get into the car doesn't mean they aren't in there. The camera cuts away from the villains as they get in the car (to show Johnny's ineptitude with a gun) - the other villain gets in off-camera.
The camera does cut away from the villains to show Johnny's ineptitude with a gun slightly earlier, howeverthe camera is focused on the hearse when they get into the car and as it drives off and the other villain is not present. Jump to the one-minute mark here https://www.youtube.com/watch?v=hH_gxr0tZ6Y.
Correction: This is true but as you stated it has to be proven. It seems that nobody was able to prove it.