The film has several logical flaws, the foremost being the two "letters of transit" which enable their bearers to leave Vichy French territory. According to the audio , Ugarte says the letters had been signed by (depending on the listener) either Free French General Charles de Gaulle or Vichy General Maxime Weygand. The English subtitles on the official DVD read de Gaulle, while the French ones specify Weygand. Weygand had been the Vichy Delegate-General for the North African colonies until November 1941, a month before the film is set. De Gaulle was the head of the Free French government in exile, so a letter signed by him would have provided no benefit. A classic MacGuffin, the letters were invented by Joan Alison for the original play and never questioned. Rick suggests to Renault that the letters would not have allowed Ilsa to escape, let alone Laszlo: "People have been held in Casablanca in spite of their legal rights."
In the same vein, though Laszlo asserts that the Nazis cannot arrest him, saying, "This is still unoccupied France; any violation of neutrality would reflect on Captain Renault," Ebert points out, "It makes no sense that he could walk around freely. ... He would be arrested on sight." Harmetz, however, suggests that Strasser intentionally allows Laszlo to move about, hoping that he will tell them the names of Resistance leaders in occupied Europe in exchange for Ilsa being allowed to leave for Lisbon.
In addition, no uniformed German troops were stationed in Casablanca during World War II, and neither American nor French troops occupied Berlin in 1918.
According to Harmetz, few of the refugees portrayed would have gone to Casablanca at the time portrayed. The usual route out of Germany was via Vienna, Prague, Paris, and London. Others tried to go from Paris through the Pyrenees to Spain. The film's technical advisor, Robert Aisner, traced the path to Morocco shown in Casablanca's opening scene.