Enquire within upon everything The great Victorian-era domestic standby
viii. A player cannot castle under any of the following
circumstances:--1. If he has moved either King or Rook. 2. If the King be in check. 3. If there be any piece between the King and the Rook. 4. If the King, in moving, pass over any square commanded by any one of his adversary's forces.
[You cannot castle to get out of check.]